Rainbow Layer Cake with Buttercream Roses

A dazzling six-layer vanilla sponge cake tinted the colors of the rainbow and finished with a garden of piped buttercream roses. Moist, tender crumb inside; silky frosting outside—this showpiece turns any occasion into a celebration.

Why You’ll Love This Recipe

• Striking rainbow interior and sculpted floral exterior in one dessert

• Straightforward butter-based batter—no specialty methods required

• Reliable American buttercream that holds its shape for detailed piping

• Easily scalable: bake all six layers at once or in two rounds

• Flavor-first: delicate vanilla cake balanced by subtly sweet frosting

Ingredients

(Tip: You can find the complete list of ingredients and their measurements in the recipe card below.)

Vanilla Rainbow Cake (six 8-inch layers)

4 ½ cups cake flour
2 ½ teaspoons baking powder
½ teaspoon baking soda
1 teaspoon fine salt
1 ½ cups unsalted butter, room temperature
3 cups granulated sugar
6 large egg whites, room temperature
3 large whole eggs, room temperature
2 tablespoons pure vanilla extract
2 ¼ cups buttermilk, room temperature
Gel food coloring: red, orange, yellow, green, blue, violet

American Buttercream & Decoration

2 ½ cups unsalted butter, room temperature
10 cups powdered sugar, sifted
6 tablespoons heavy cream, plus more as needed
2 teaspoons pure vanilla extract
Pinch of salt
Gel food coloring for roses (e.g., pink, peach, lavender, teal)

Directions

1. Prep ovens & pans – Preheat to 350 °F (177 °C). Grease six 8-inch round pans, line bottoms with parchment, and lightly flour.

2. Combine dry ingredients – Whisk flour, baking powder, baking soda, and salt; set aside.

3. Cream butter & sugar – Beat butter and sugar on medium-high until pale and fluffy, 3–4 minutes.

4. Add eggs – Blend in egg whites one at a time, then whole eggs, scraping bowl. Mix in vanilla.

5. Alternate dry and buttermilk – On low speed, add flour mixture in three parts, alternating with buttermilk, beginning and ending with flour. Stop as soon as batter is smooth.

6. Portion & tint – Divide batter evenly into six bowls (about 2 cups each). Tint each bowl a different rainbow hue, stirring gently until color is uniform.

7. Bake – Pour tinted batters into prepared pans. Bake 20-24 minutes, rotating halfway, until a tester comes out clean. Cool 10 minutes; turn out and cool completely.

8. Make buttercream – Beat butter until creamy. Add half the sugar, mix on low, then the remaining sugar, cream, vanilla, and salt. Increase speed and whip 3 minutes until light. Adjust cream for spreadable consistency.

9. Color frosting – Reserve about 3 cups white frosting for crumb coat. Tint remaining frosting in rose shades; fit piping bags with 1M or 2D tips.

10. Assemble layers – Level cakes if domed. Stack from violet to red, spreading about ¾ cup white buttercream between layers.

11. Crumb coat – Cover entire cake with a thin layer of white buttercream; chill 20 minutes.

12. Final coat – Apply a smooth, thicker layer of white buttercream. Chill again briefly.

13. Pipe roses – Starting at the base, pipe tight spirals to form roses, working upward and alternating colors for a natural bouquet effect. Cover top last.

14. Serve – Allow cake to come to room temperature 30 minutes before slicing for best texture.

Servings and Timing

• Yield: 16 generous slices (8-inch × 6-layer cake)

• Active prep: ~1 hour 30 minutes

• Baking: 20–24 minutes per batch

• Cooling & decoration: ~1 hour 30 minutes

• Total time: ~4 hours

Variations

• Swiss-meringue buttercream – Swap American icing for a lighter, less-sweet finish.

• Chocolate rainbow – Substitute ½ cup flour with Dutch cocoa in each layer and deepen colors slightly.

• Gluten-free option – Use a 1:1 gluten-free baking flour plus 1 teaspoon xanthan gum.

• Single-bowl sheet cake – Bake tinted batter sequentially in a 13 × 18-inch sheet pan; roll into a rainbow roulade.

Storage/Reheating

• Room temperature: Covered cake keeps 1 day at 20–22 °C.

• Refrigerator: Store slices airtight up to 5 days. Bring to room temperature before serving.

• Freezer: Wrap unfrosted layers or frosted leftovers in plastic plus foil; freeze up to 2 months. Thaw overnight in fridge, then 30 minutes on counter.

• Reviving buttercream: If chilled icing feels hard, whip briefly with 1-2 teaspoons cream until fluffy.

FAQs

How do I achieve vibrant colors without overmixing?

Use concentrated gel colorings and fold gently; stop as soon as color is even.

Can I bake the layers in fewer pans?

Yes. Bake in two or three pans, cool, wash, and reuse; extend total bake time accordingly.

What tip is best for buttercream roses?

Wilton 1M or 2D open-star tips create classic rosettes with minimal effort.

Why do my layers dome?

Oven too hot or overmixed batter. Bake at accurate 350 °F and avoid overbeating flour.

Can I flavor the buttercream?

Replace 1 teaspoon vanilla with almond, lemon, or rosewater extract for a subtle twist.

How far in advance can I assemble?

Fully decorated cake holds 24 hours refrigerated; pipe roses the same day for freshest look.

My frosting is too stiff—what now?

Beat in cream 1 teaspoon at a time until spreadable. Conversely, chill briefly if too soft.

Is buttermilk essential?

Yes—it tenderizes the crumb. Substitute 2 ¼ cups whole milk plus 2 tablespoons lemon juice, rested 10 minutes.

How do I level the cakes evenly?

Use a long serrated knife or cake leveler; spin the layer on a turntable while cutting.

Can I use natural food dyes?

Powdered or paste plant-based dyes work, but hues will be softer—add a touch more for intensity.

Conclusion

This Rainbow Layer Cake with Buttercream Roses pairs playful color with refined piping to create a dessert that’s as memorable on the palate as it is on the plate. Follow the clear steps above, and you’ll unveil a spectrum of flavor, texture, and visual delight in every slice—no special occasion required, merely the desire to celebrate in technicolor.