Combine Dry Ingredients: In a large bowl, whisk together flour, baking powder, baking soda, cinnamon, and salt. Stir in the finely chopped rhubarb to coat. Set aside.
Mix Wet Ingredients: In a separate bowl, mix brown sugar, granulated sugar, eggs, melted and cooled butter, vanilla extract, orange zest, and sour cream until smooth.
Combine Wet and Dry: Add the wet mixture into the dry ingredients. Stir gently until the flour is fully incorporated. Do not over-mix. The batter will be thick.
Prepare Streusel: In a small bowl, mix brown sugar, white sugar, flour, softened butter, and cinnamon with a fork until the mixture becomes crumbly.
Fill Muffin Tins: Spray a 12-muffin tin with non-stick cooking spray, use liners, or make homemade tulip liners. Divide the batter evenly among the cups. I use a 3.25-ounce scoop for precision. Sprinkle streusel on top of each muffin.
Bake: Place the muffins in the preheated oven for 7 minutes at 425°F. Then reduce the temperature to 350°F and continue baking for 12 to 14 minutes, or until a toothpick inserted in the center comes out clean.
Glaze: While the muffins are baking, whisk together confectioner’s sugar, orange juice, and orange zest. Drizzle the glaze over the muffins right after they come out of the oven for a thin glaze, or wait until they cool for a more pronounced drizzle.
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Notes
Recipe makes 12 large muffins easily if using tulip liners. If using regular muffin liners, you may want to distribute amongst 14 muffins so there is no spillage.