Combine the cornstarch and water to make a slurry in a bowl. Mix the strawberries and sugar in a pan. Cook over low heat until the strawberries release their juices about 5 minutes, then add the cornstarch mix and stir until well combined. Stir for another minute or two until it has thickened. Remove from heat. Let cool to room temperature while you prepare the rest of the cake.

Beat the cream cheese on medium speed for about 30 seconds until smooth. Add in the sugar, egg and lemon juice and beat until well combined. Set aside.

Preheat the oven to 350F. Butter a 9" round cake pan. Line the pan with a circle of waxed paper cut to fit and then butter the paper and the sides of the pan.

Combine the flour and sugar together in a bowl. Using a pastry cutter or just 2 forks, cut in the butter until the mixture resembles coarse crumbs. Measure 3/4 cup of the mixture and set aside. Add the baking soda, baking powder and salt and mix well.

In another bowl, beat the sour cream, egg and vanilla extract until well blended. Using a hand whisk or a spoon, stir gently into the flour mixture until just incorporated. Batter may be a bit lumpy. Set aside.

Spread the batter in the pan, with about 1/2 inch up the sides, also leaving a 1/2 inch border around the edges bare (like making a well). Pour the cream cheese mixture over the batter, being careful not to go beyond the border. Spread the strawberry jam on top of the cream cheese mixture. Sprinkle the remaining 3/4 cup crumbs over the strawberry filling. Bake for 50-55 minutes. Cool in the pan on a wire rack for 20 minutes before removing the cake.

Slice strawberries and put into a mixing bowl; add the sugar and mix; allow them to sit for at least 5 minutes.

If desired and you want to top the cake with more berries; slice the strawberries and add sugar to them. Let them sit for 10-15 minutes until their juices run. Spoon atop cake slices.