TO BAKE THE CAKE: PREP PAN - Spray with Pam. Line the bottom of an 8" diameter x 2 1/2" deep round cake pan with a parchment round. Brush parchment and insides of the pan with soft butter and dust with sugar.

PRE-HEAT OVEN: To 325°F (163°C).

MIX: In Kitchen Aid mixer using the paddle, cream butter on medium speed until smooth and creamy, about 1 minute. Gradually add sugar, then scrape down the bowl. Turn to high speed and beat until light and fluffy, about 5 minutes.

On medium speed, add the eggs a little at a time until incorporated, then the sour cream, milk, zests, and vanilla, scraping down the bowl as needed. Mix well. The mixture may look a little curdled at this point, especially if the dairy ingredients are not at rook temperature. The batter will smooth out when the flour mixture is added.

Sift together the flour, cornstarch, salt, baking powder, and baking soda.

On low speed, slowly add the flour mixture to the mixer bowl and mix just until smooth, about 30 seconds. Scrape up the bottom of the bowl and mix in.

Transfer the batter to the prepared cake pan and place on a quarter or half sheet pan

BAKE: At 325º F (163°C) for about 55 minutes, or until golden brown and the sides of the cake start to pull away from the pan. Do not test with a cake tester or wooden skewer until the cake is almost done. Doing so too soon will cause the cake to deflate in the center. Wait to do this doneness test until the center of the cake looks completely puffed.

Cool in pan about 10 minutes. Unmold while still warm, and place on parchment lined sheet pan to finish cooling. Refrigerate the cake so that it is cold before filling; it will be more stable if chilled.

When cold, split the cake in half horizontally, using a cake leveler or a serrated knife.

STRAWBERRY FILLING: Divide the strawberries in half. Crush half the strawberries with a fork or a potato masher and stir in the 60g sugar. Leave the other half as is, in quarters.

WHIPPED CREAM: Whip cream softly in Kitchen Aid, using the whisk. Stop when you can start to see marks in the cream. It's easy to overwhip. Finish whipping by hand with a whisk.

ASSEMBLE THE SHORTCAKE: Place the bottom layer of cake on a platter or cake stand. Place strips of parchment paper around the cake to catch drips. Scatter about 2/3 of the quartered strawberries over the cake and spoon on about 2/3 of the crushed strawberries. Place dollops of whipped cream (using about 2/3 of the cream) and spread a thick layer of cream over the strawberries allowing some of it to slightly ooze over the edge. Place the top layer of cake on the whipped cream. Dust the top of the cake with powdered sugar. Again, place big dollops of whipped cream on top of the cake. Scatter the rest of the strawberries over the cream and drizzle with crushed strawberries. If a little drips over the sides, it's OK Pull out the parchment strips and discard.

Shortcake filled with fresh berries and whipped cream is best served the same day, but the cake can be made ahead to save time on serving day.

IF MAKING AHEAD: Freeze first on a quarter sheet pan or large flat plate until frozen then place in a large plastic bag and keep frozen until needed. This cake freezes well.

If desired, or short on time, leave the cake whole and cut in wedges: Serve the fresh strawberries on the side with dollops of whipped cream.