Zest the lemon and set aside. In the saucepan on the medium heat, add cherries, 2 tbsp of lemon juice, 1 cup of sugar, cornstarch and cinnamon.
Bring to a boil, and cook for 8 minutes or unit mixture thickened. Remove from the heat and cool.
Preheat the oven to 355°F. Line and butter 11 inch x 1.125 inch round tart pan.
Combine all purpose gluten free all-purpose flour, baking powder and salt.
In a separate bowl, beat butter with ¾ cups of sugar until creamy. One by one add egg yolks, then sour cream, vanilla and zest of lemon.
Add dry ingredients, and mix until combined. Dough should be thick.
Transfer the dough to the tart pan and press with hands to form edges. It helps to oil hands to prevent dough from sticking.
Add cherry filling on the top and bake for 30 minutes.
While the tart is baking beat egg whites until stiff peaks then add sugar and beat until sugar dissolved.
After 30 minutes take out the tart from the oven, spread meringue on the top and bake for another 20 minutes.
Cool completely before serving.