Step 1: Preheat and Prepare
Preheat your oven to 350°F (175°C). Grease a 9×13 inch baking dish with butter or non-stick spray.

Step 2: Create the Zesty Lemonade Filling
Zest 2-3 of the lemons until you have about 2 tablespoons of packed zest. Then, juice all the lemons until you have 1 cup of fresh lemon juice. In a large bowl, whisk together the 1 ½ cups of granulated sugar and the eggs until the mixture is pale and slightly thickened. Gradually whisk in the melted butter, followed by the fresh lemon juice, lemon zest, and vanilla extract. Finally, whisk in the ⅓ cup of flour and salt until the mixture is smooth and no lumps remain. If using, whisk in the yellow food coloring. Pour this vibrant lemon filling into the prepared baking dish.

Step 3: Prepare the Sugar Cookie Dough Topping
In a medium bowl, whisk together the 2 ½ cups of flour, baking powder, and salt. Set aside. In the bowl of a stand mixer fitted with a paddle attachment (or with a hand mixer), cream the softened butter and 1 ¼ cups of sugar together on medium speed until light and fluffy, about 2-3 minutes. Beat in the egg and vanilla extract until combined. Gradually add the flour mixture to the wet ingredients, mixing on low speed until just combined. The dough will be thick. Add the milk or sour cream and mix until a soft, cohesive cookie dough forms.

Step 4: Assemble the Crumble
Using your hands, tear off small pieces of the sugar cookie dough and flatten them slightly. Drop these pieces evenly over the entire surface of the lemon filling. You don’t need to cover it completely; leave some gaps for the lemon filling to bubble up and peek through. The topping will spread and merge as it bakes.

Step 5: Bake to Golden Perfection
Place the baking dish in the preheated oven and bake for 40-50 minutes, or until the sugar cookie topping is golden brown, set, and a toothpick inserted into the center of the topping comes out clean. The lemon filling below will still be jiggly—this is normal and it will set further as it cools.

Step 6: The Crucial Cooling Period
This is the hardest but most important step. Remove the crumble from the oven and place it on a wire rack. Allow it to cool for at least 1-2 hours before serving. This cooling time is essential for the lemon filling to thicken and set properly. If you cut into it too early, the filling will be runny.

Step 7: Serve and Enjoy
Scoop warm portions into bowls. Top with a generous scoop of vanilla ice cream, which will slowly melt into the warm, tangy lemon filling and buttery cookie topping, creating the ultimate bite. Garnish with fresh berries and a sprinkle of lemon zest for a beautiful and flavorful finish.