In a mixing bowl, combine all-purpose flour, granulated sugar, and lemon zest until well blended. Cut in cold unsalted butter with a pastry cutter or fork until the mixture resembles coarse crumbs. Transfer to fridge while preparing cake batter.

In a medium bowl, beat softened cream cheese and granulated sugar together with an electric mixer until creamy and smooth. Add one egg and fresh lemon juice, mixing until fully incorporated. Set aside.

Preheat oven to 350°F (175°C) and grease an 8-inch round cake pan. In a large bowl, whisk together dry ingredients including flour, baking powder, and salt, mixing in the lemon zest. Cream unsalted butter and granulated sugar until light, add egg and lemon juice. Alternate mixing in dry ingredients and milk until just combined.

Spoon half of the lemon cake batter into prepared pan, smoothing into an even layer. Pour cream cheese filling over the batter, spreading nearly to edges. Top with remaining cake batter and sprinkle crumb topping over the top. Bake for 30-35 minutes until edges are golden and a toothpick comes out clean.

Remove cake from oven and cool in the pan on a wire rack for about 15 minutes. Transfer cake to the rack and let it cool completely before slicing.