• Preheat the oven to 425°.
• Combine the sugar, cornstarch, cinnamon, nutmeg, and salt.
  1 c. sugar, 3 Tbsp. cornstarch, 1/2 tsp. ground cinnamon, 1/4 tsp. nutmeg, pinch of salt
• Add the sour cream and beaten egg, and mix well.
  1 c. sour cream, 1 large egg, beaten
• Gently fold in the chopped rhubarb. Mix to combine.
  3 c. chopped fresh rhubarb (or thawed frozen rhubarb)
• Pour the rhubarb mixture into an unbaked 9" pie crust.
  1 (9") unbaked pie crust
• Spread the crumb mixture over the top.
• Bake in the middle (or just below the middle) of the oven, at 425°, for 15 minutes.
• Reduce the temperature to 350° and continue baking for another 40 minutes or until the topping is golden.
• Cool and enjoy or chill for later. Refrigerate any leftovers.

Crumb Topping:

• Combine the oats, flour, brown sugar, and zest.
  1/2 c. quick-cooking oats, 1/2 c. all-purpose flour, 1/3 c. brown sugar, 1/2 tsp. zested orange or lemon peel, 1/3 c. butter (approx. 6 Tbsp.)
• Cut in the butter until crumbly. Or melt the butter and mix it in until crumbly. (Either way works.)
• Sprinkle the crumb topping all over the top of the rhubarb mixture.