Preheat the oven to 350 degrees F (175 degrees C).

Grease a 9-inch springform pan and set aside.

In a mixing bowl, prepare the crumb topping by combining 1 1/2 cups flour, 1 cup sugar, 2 tablespoons lemon zest, 1 teaspoon lemon juice, and 1/4 teaspoon salt.

Cut in cold butter until the mixture resembles coarse sand.

Set aside.

In another bowl, combine 1 1/2 cups flour, baking soda, and 1/4 teaspoon salt.

In a large mixing bowl, beat 1/2 cup butter and 1 cup sugar until creamy.

Add eggs one at a time, beating after each addition.

Add lemon extract, vanilla, 2 tablespoons lemon zest, and 1/4 cup lemon juice.

Gradually add the dry ingredients and mix just until all ingredients are moistened.

Spread the batter into the prepared pan, then top with lemon curd.

Sprinkle the crumb mixture evenly over the top.

Bake in the preheated oven for 35 to 40 minutes or until a toothpick inserted near the center comes out clean.

Let cool on a wire rack.

Remove the springform pan and sprinkle confectioner’s sugar over the top of the cake if desired.