Wash, cut, and freeze the fresh rhubarb. Or use frozen rhubarb. After the fresh rhubarb is frozen, remove and defrost in a colander. Discard the liquid that is released.
3 cups rhubarb (fresh or frozen)
Preheat the oven to 375 degrees F. Spray a tart pan, round pizza pan, or galette pan with non stick spray. Set aside.
Make a single pie crust, or let a store bought crust come to room temperature. Roll or lay out flat on the prepared pan.
1 pie crust (purchased or homemade)
In a large mixing bowl, measure out the sugar, cornstarch, and salt and mix together. Add the lemon zest, defrosted and drained rhubarb, and lemon juice. Mix well.
3 cups rhubarb (fresh or frozen), 1 cup sugar, ¼ cup cornstarch, ¼ teaspoon salt, 2 tablespoon lemon juice, 1 teaspoon lemon zest
Pour the fruit and sugar mixture onto the center of the pie crust. Gently gather up the outer few inches of the pie crust and bring in toward the center of the pie. Pinch together every few inches so that the pie crust stays in position around the fruit mixture. Brush butter, milk, or cream onto the raw pie crust. Sprinkle entire galette with the coarse grain pastry or sanding sugar.
2 tablespoon butter, melted, 3 tablespoon coarse pastry or sanding sugar (optional)
Place the pan with the prepared galette in the oven. Bake approximately 35 to 38 minutes, checking at 35 if your oven runs hot. Remove when the galette is bubbly in the center and the crust golden brown.