Preheat oven to 375F. Make the crust by mixing the three ingredients (reserve a couple of tablespoons of flour for rolling out). Start by adding slightly less Greek yogurt and adding more if needed until a dough forms. If dry, add a splash of water to bring the dough together.
Gently knead the dough in the bowl for about a minute until smooth, then transfer to a piece of lightly floured parchment paper and roll it out thinly, large enough to cover a 9.5-inch pie dish. (If sticky, refer to the tips section).
Transfer the rolled-out dough to a greased 9.5-inch pie dish and peel the parchment away. Put a new piece of parchment and fill it with pie weights (such as dried beans or rice). Bake the shell for 15 minutes, then remove the weights and parchment. Poke with a fork and bake for about 5 more minutes or until the surface is set.
To prepare the filling, add the apples to a large pot and cook over medium heat to release some of their moisture (about 3 to 5 minutes). Then, add the remaining ingredients and cook for a few more minutes, stirring constantly. This will help eliminate the raw taste of the flour and slightly soften the apples. Taste the mixture and adjust the cinnamon or sweetener according to your preference.
For the crumb topping, mix all of the ingredients with your hands until a crumbly mixture forms. You don’t want to overmix because a dough will form.
Transfer the apple filling to the empty crust and then sprinkle the crumb topping over the top. The crust edges will likely already be golden enough, so wrap the edges of the pie in foil or use a pie crust shield to protect them.
Bake the pie for 40-50 minutes, until the apples feel fork tender and the topping is baked through. If needed, you can broil on low at the end of baking to give the topping a deeper golden color.
Allow the pie to rest for 1-2 hours before slicing into it so it can set.