To make crumb cake topping, combine 1 1/2 cups flour, 3/4 cup sugar, 1 1/2 teaspoons cinnamon, 3/4 cup cold, chopped butter and 1 teaspoon vanilla in a food processor. The crumb topping is mixed well once large clumps form. Keep the topping in the refrigerator until ready to use.
For a cake recipe to use with the crumb topping, combine a 1/4-ounce package active dry yeast, 1/4 cup warm milk and 1 tablespoon sugar in an electric mixer. Let it stand for five minutes until the mixture begins to foam. Separately, stir together 3/4 cup warm milk and 1 tablespoon lemon juice, then let it sit for one to two minutes until curdled. Mix 3 3/4 cups flour into the yeast mixture, then add 1 1/2 teaspoons salt, 2 room temperature eggs, 1 1/2 teaspoons vanilla and 1/2 cup sugar. Beat in the curdled milk until a dough forms.
Beat in one piece of 3/4 cup chopped, softened butter at a time. After adding in all butter, beat the dough for an additional five to eight minutes until it is very sticky. Top with 2 tablespoons flour and cover the dough. Let the dough rise at room temperature until its size has doubled.
Spread the dough into a buttered 13-by-9-inch baking dish and top with half of the crumb topping. Cover the dough and let it rise until it doubles in size again. Top with the remaining crumb topping and bake for 55 to 60 minutes at 350 degrees Fahrenheit.