Combine chopped strawberries, lemon juice, and sugar in a small saucepan over medium heat. Cook for 4–5 minutes, stirring occasionally, until the strawberries soften and begin to break down.

In a separate small bowl, whisk together cornstarch and water until smooth. Pour this mixture into the saucepan. Cook for another 2–3 minutes until the filling thickens. Set aside to cool completely.

Preheat the oven to 350°F (175°C). Grease two 8-inch round cake pans and line the bottoms with parchment paper.

In a large mixing bowl, whisk together eggs, buttermilk, oil, brewed coffee, and vanilla extract until smooth and fully combined.

In another bowl, sift together all-purpose flour, both regular and Dutch-process cocoa powders, baking soda, baking powder, salt, and granulated sugar. Gradually add the dry mixture to the wet ingredients, stirring just until the batter is smooth. Avoid overmixing.

Divide the batter evenly between the prepared pans. Bake for 30–35 minutes, or until a toothpick inserted into the center comes out clean. Cool the cakes in the pans for 10 minutes, then transfer them to wire racks to cool completely.

In a mixing bowl, beat softened butter on medium speed for 2–3 minutes until creamy. Add freeze-dried strawberry powder, lemon juice, vanilla extract, and a pinch of salt. Mix until fully incorporated.

Slowly add powdered sugar, one cup at a time, mixing on low speed. Gradually pour in the heavy cream, mixing until the frosting reaches your desired consistency. Beat on medium-high speed for 3–5 minutes until light and fluffy.

If needed, level the cooled cake layers with a serrated knife. Place one layer on a cake board or serving plate. Spread a generous layer of the cooled strawberry filling over the top. Place the second cake layer on top.

Cover the top and sides of the cake with strawberry buttercream. Use a spatula or cake scraper to smooth the surface. Optionally, garnish with fresh strawberries, chocolate curls, or sprinkles. Refrigerate briefly to set if needed before serving.