Preheat the oven to 350 degrees F. Grease an 8-inch square baking pan with butter.

Combine the melted butter and the gingersnap crumbs. Press the mixture into the bottom of the baking pan.

In a large saucepan over medium heat, combine the sugar, cornstarch, lemon juice, and sour cherries.  Cook the cherries, stirring occasionally, until they soften and the juice thickens, about 10-15 minutes. Pour the cherries on top of the gingersnap crust.

Using an electric mixer beat the ricotta, cream cheese and sugar in a large bowl until smooth. Add the eggs one at a time fully mixing after each addition. Stir in the vanilla extract. Pour the batter over the cherries using a spatula to spread in an even layer.

Bake for 30 minutes until the cheesecake has puffed up and is still slightly wobbly in the center. Cool to room temperature before covering and chilling in the refrigerator. Cut into 16 2-inch square bars and serve cold.