Preheat oven to 350°. Cut 3 (9-inch) cardboard cake rounds into quarters. Line a 17x12-inch rimmed baking sheet with parchment paper. Spray with cooking spray.
In a large bowl, beat together butter and sugar with a mixer at medium speed until fluffy, 3 to 4 minutes, stopping to scrape sides of bowl. Add jam, beating to combine. Add eggs, one at a time, beating well after each addition. Beat in vanilla extract and enough food coloring to achieve desired shade of pink.
In a medium bowl, whisk together flour, baking powder, salt, and baking soda. With mixer at low speed, gradually add flour mixture to butter mixture alternately with buttermilk, beginning and ending with flour mixture, beating just until combined after each addition. Spread batter into prepared pan. Tap pan on counter several times to reduce air bubbles.
Bake until a wooden pick inserted in center comes out clean, approximately 15 minutes. Let cool completely in pan.
Using a 2¼-inch round cutter, cut rounds from cooled cake. Place one cake round on a cardboard quarter, and spread 1 teaspoon Strawberry Buttercream on top. Top with another cake round, pressing cakes together. Repeat with remaining cake rounds and cardboard quarters.
Place remaining Strawberry Butter-cream in a piping bag fitted with a small petal tip (Ateco #101). With wider end of tip toward bottom and referring to Step by Step Guide below this recipe, pipe vertical rows of ruffles around sides of cakes, starting at bottom and working upward. Pipe concentric ruffles on top of cake. Freeze cakes on cardboard quarters in an airtight container for up to 1 week. (Cakes will be easier to work with when frozen.)
To serve, slide a thin spatula beneath frozen cakes to separate them from cardboard quarters, and place cakes on paper doilies on individual cake stands or serving plates. Let come to room temperature.
Garnish with crystallized flowers, if desired.
Notes
*We used Wilton No Taste Red.
Recipe by TeaTime Magazine at https://teatimemagazine.com/strawberry-ruffle-cakes-recipe/