Preheat the oven to 350°F. Butter the bottom of three 7-inch round pans and line with baking paper.

In the bowl of an electric mixer, mix together the cake flour, sugar, baking powder, baking soda, Houjicha powder, and salt on low speed with the paddle attachment for 1 minute.

Keeping the mixer on low speed, add the cubed butter and combine until the mixture resembles coarse sand (about 4 minutes).

In a separate bowl, whisk together the oil, eggs, buttermilk, and vanilla. With the mixer on low speed, gradually add the wet ingredients and mix just until combined.

Weigh out equal amounts into 3 7-inch cake pans. Tint the cakes with food coloring (I used Wilton’s blue, pink and violet). Bake for about 32-35 minutes or until a toothpick inserted into the center comes out clean. Let the cakes cool completely before decorating.

To make Swiss Meringue buttercream:

In a large saucepan, place mixing bowl over a pot of barely simmering water. Add egg whites and cups sugar and whisk together until frothy. Whisk constantly until mixture reaches 160˚F (takes about 3 min). Sugar should be fully dissolved (no granules when rubbing mixture between finger tips). Mixture will feel hot to the touch (or like the temperature of warm milk).

Once bowl is at room temperature, switch to paddle attachment, reduce to medium speed and add butter 1 Tbsp at a time, adding it just as fast as it is absorbed by meringue. Once all butter is in, scrape down the bowl and continue beating until it reaches a thick whipped consistency (3 min on med-high speed). If it looks lumpy or liquidy at all, keep beating until smooth, thick and whipped. Add 2 tsp vanilla extract and 1/4 tsp salt and mix on med-high until incorporated.

Fix mixer with the whisk attachment. Whip on medium high speed until smooth and creamy. Begin adding room temperature butter, a few slices at a time. Add the salt and continue to whip until all the butter has been incorporated. Switch the paddle attachment and beat for a few more minutes, until the frosting is silky.

To make Lemon Curd:

Peel 3 lemons, taking as little of the bitter white pith as possible. Cut all the lemons in half, juice them, and measure out 1/2 cup of juice.

Combine the sugar and lemon peels in the bowl of a food processor and process until the peels are ground very fine, about 30 seconds. Add the butter, egg yolks, lemon juice and salt to the bowl. Pulse a few times and then process for 15 seconds or so to incorporate everything.

Pour mixture into a small saucepan and place over very low heat. Stir frequently, using a heat-proof spatula. Do not leave the mixture unattended as it is very easy for it to overcook and curdle. Cook until the mixture begins to thicken, 12-15 minutes (170˚F if using thermometer). You can also test the curd by coating the back of a spoon with the curd and running a finger through it. It should leave a clear, distinct path.

Pour the curd through a strainer to catch any peel and coagulated egg. Allow to cool to room temperature, then seal the jar and store in your refrigerator.

To Assemble and Decorate:

Trim off excess of the layers (freeze before hand helps). Place first first layer on cake board, making sure to frost between each layer and crumb coat. In between each layer, create a ring of buttercream and fill with lemon curd and passionfruit jam. Use a cake turntable to smooth white frosting over entire cake. Add in an ombre green layer if desired.

Attach the flowers on the cake by washing it, wrapping in saran wrap and putting the stalk through bubble tea straws. Arrange properly before inserting into the cake. Refer to video tutorial by Rosie’s Dessert Spot for other idea inspirations.