Preheat the oven to 350°F. Prepare three 8-inch round baking pans, line the bottom with parchment paper, and grease the sides.

In a large mixing bowl, combine the sugar, vegetable oil, eggs, and vanilla extract. Beat on medium speed until well incorporated, about 2 minutes.

Mix in the sour cream and beat until well combined.

Combine the dry ingredients in a separate bowl. Add half the dry ingredients and beat on low speed while pouring in half of the milk.

Add the remaining dry ingredients, mixing on low while pouring in the remaining milk.

Divide the batter evenly between the three pans. Bake at 350°F for 20-23 minutes.

Test for doneness with a toothpick. Allow to cool completely.

Chop and puree the strawberries.

Combine the flour and sugar in a saucepan, then add pureed strawberries and lemon juice.

Cook over medium-high heat until boiling, then reduce heat and simmer until thickened.

Allow puree to cool completely.

Chill the mixing bowl and whisk attachment in the freezer.

Beat mascarpone and slowly add heavy cream until liquid consistency.

Increase speed and beat until soft peaks form.

Add powdered sugar and vanilla, beating until stiff peaks form.

Cut the domes off the top of the cake layer.

Pipe frosting around the edge, then spread half of the strawberry mixture over the cake.

Pipe another thin layer of frosting on top and add the second layer of cake.

Repeat with the remaining strawberry sauce and final layer of cake.

Fill in gaps with frosting and crumb coat the cake.

Frost the top and sides of the cake.

Pipe florets on top and garnish with leftover strawberries. Refrigerate.