Start by preheating your oven to 350 degrees and spray a 9 x 13 baking pan with non-stick spray or grease with butter.
Peel and slice apples into 1/4 inch slices and add apples to a large mixing bowl. To the apples, add 3 tablespoons melted butter, 2 tablespoons all purpose flour, water, sugar, vanilla, cinnamon, a squeeze of lemon and salt then mix to combine.
In a separate bowl, combine brown sugar, cinnamon, oats and flour. Using a sharp knife, cut the cold butter into small pieces. Add the cut up cold butter to the flour mixture and using your fingers, fork or pastry cutter, cut or rub butter into the flour mixture until it comes together to form crumbles. Stir in chopped pecan pieces to your crumble topping.
Transfer your apples to your prepared baking pan and sprinkle the apple crisp topping evenly over the apples. Bake for 40-45 minutes or until golden brown.
Remove from oven and let cool slightly before serving with a big scoop of vanilla ice cream.. (ice cream is optional but highly recommended).