In a medium-sized bowl, combine ¼ cup all-purpose flour, ¼ cup brown sugar, and ¼ teaspoon ground cinnamon. Cut in 2 tablespoons salted butter, with a pastry blender or your hands until the mixture becomes crumbly. Set aside.
Cake
Preheat the oven to 350 degrees Fahrenheit. Spray an 8-inch springform pan or an 8-inch round cake pan with nonstick cooking spray. Set aside.
In a clean medium-sized bowl, whisk together 1 ¼ cup all-purpose flour, ½ teaspoon baking powder, ¼ teaspoon baking soda, and ⅙ teaspoon salt.
Combine ⅔ cup powdered sugar and ¼ cup softened unsalted butter in a large bowl using a hand mixer or a stand mixer fitted with the paddle attachment.
Add ½ teaspoon vanilla extract and 1 large egg. Add 6 tablespoons milk and 2 tablespoons lemon juice; beat for 2 minutes. Add the flour mixture to the sugar mixture, and beat just until smooth.
Spoon half of the batter into the prepared pan, spreading evenly. Top with 1 cup strawberry jam. Spoon the remaining batter over the strawberry layer. Sprinkle with crumb topping.
Bake for 40-45 minutes or until a toothpick inserted into center comes out clean.
Cool for 10 minutes before removing the sides from the springform pan. Cool completely on a cooling rack.