Place the cherries in a strainer and run cold water on them. When the cherries show their color and (if frozen) are almost defrosted, drain and place them at the bottom of a pie dish and spread small pieces of butter all over the cherries.
Combine Greek yogurt, sour cream, instant pudding, lemon zest, egg yolks, vanilla, cornstarch, and water in a bowl and whisk until smooth.
Add two tablespoons of sugar to the egg whites and whisk it quickly for
Add the egg whites to the cheese filling and blend them well using the whisk or large spatula in folding motions.
Pour the filling on top of the cherries making sure the filling reaches the bottom.
Bake at 350° for 15 minutes, then lower the heat to 325° and continue baking for another 45 minutes.
Remove from the oven, let cool, sprinkle with powdered sugar and refrigerate overnight.