Serves 6 to 8
6 tablespoons cold butter, cut into small pieces, plus more for greasing pan
2-1/2 to 3 pounds rhubarb, trimmed and cut into 1/2 inch pieces (about 5 to 6 cups)
1/4 cup granulated sugar
1 teaspoon orange or lemon zest
1 tablespoon orange or lemon juice
Topping:
1/2 cup flour
1/2 cup rolled oats (not quick oats)
1/2 cup brown sugar
1/2 teaspoon salt
1/3 cup butter, cut into cubes
In a bowl, mix all of the topping ingredients with a fork until well combined and refrigerate while making the rhubarb filling.
Preheat the oven to 375 F. degrees. Butter a 8 or 9 inch baking dish (I used a 11 x 7 inch glass baking dish). Toss rhubarb with white sugar, orange or lemon zest and just pour out into baking dish, leveling it as best as possible.
Sprinkle crumble topping over rhubarb as evenly as possible. You may have extra, which can be refrigerated for a future crumble topping dessert.
Bake for 45 to 50 minutes or until top is golden and beginning to brown and rhubarb is bubbling. Remove from oven and allow to cool. Best if eaten while slightly warm but may be made in the morning and refrigerated. Take out of refrigerator and allow to come to room temperature before serving or warm slightly in a 350F oven for about 20 minutes.
Serve with a scoop or two of vanilla ice cream.