Healthy Rhubarb Crumble Pie
- 1 pre-made pie crust
- 6 tablespoons all-purpose flour, split
- 2/3 cup granulated sugar, plus 1 tablespoon set aside
- 5 cups diced fresh rhubarb
- Zest of 1 lemon (optional)
- 1/3 cup all-purpose flour
- 3 tablespoons packed brown sugar
- 3 tablespoons granulated sugar
- 1/2 teaspoon ground cinnamon
- 1/3 cup chilled butter