Preheat oven to 350 degrees.

In a small saucepan whisk together ¼ cup sugar and cornstarch. Stir in cold water and lemon juice. Add diced strawberries.

Stir mixture over medium heat, just until it reaches a light boil. Reduce heat to low and cook 1 minute more, stirring constantly. Remove from heat and set aside to cool.

In a medium size mixing bowl add ⅓ cup flour, 1 ½ Tbsp sugar and 2 ½ Tbsp butter. Cut ingredients together with a pastry blender until fluffy and well combined. Add brown sugar and stir with a fork. Set aside.

In a small bowl stir together 1 ¾ cup flour, baking powder, baking soda and salt. In another mixing bowl add 7 Tbsp softened butter and 1 cup sugar.

Beat with electric mixer for several minutes, until mixture is pale and fluffy. Mix in egg and vanilla. Stir in the sour cream.

Add the dry ingredients alternating with buttermilk in two separate batches and mix just until combine. (Don't overmix!)

Evenly spread ½ of the cake batter into a greased 8x8 baking dish. Spoon strawberry mixture over batter layer and gently spread evenly.

Dollop remaining cake batter by the spoonfuls over strawberry mixture and gently spread batter into an even layer. Sprinkle the crumb topping evenly over the top of the cake.

Bake at 350 degrees F for 50-55 minutes, or until toothpick inserted into center comes out clean. Allow to cool slightly before serving.