Prepare the crumb topping: In a medium bowl, toss the flour, granulated sugar, and light brown sugar. Add the softened butter and stir the mixture until it looks like coarse crumbs using a pastry cutter or your fingers. Sort aside.
Preheat your oven: Preheat your oven to 350°F (175°C), and butter or cooking spray grease a 9-inch round cake pan or springform pan. Parchment paper will also make the bottom easily removable.
Make the cake batter: Whisk together the flour, baking powder, baking soda, and salt in a large bowl. Add the lemon zest and gently stir. Beat eggs, sour cream, lemon juice, milk, and vanilla extract until smooth in another bowl. Add the wet ingredients to the dry ones gradually, stirring until just mixed.
Bake the cake: Pour the batter into the ready-made cake pan then evenly distribute it. Making sure the whole surface is covered, scatter the crumb topping over the batter. bake until a toothpick put into the middle comes out clean, 40 to 45 minutes.
Prepare the lemon glaze: To make the lemon glaze, whisk the powdered sugar and lemon juice in a small bowl until smooth while the cake bakes. Should you want more sugar or lemon juice, you can change the consistency by adding either.
Glaze the cake: Once the cake has cooled for ten minutes, drizzle the lemon glaze over top, letting it soak into the crumb topping. Let the cake cool totally before presenting it.
Serve and enjoy: Present your lemon coffee cake alongside a cup of either tea or coffee. Everyone who tastes it will be amazed since it's the ideal mix between sweet and sour!
