Blueberry Spelt Muffins

Name: Blueberry Spelt Muffins
Ingredients: Nonstick vegetable oil spray (optional); 3 Tbsp. spelt flour; 2 Tbsp. granulated sugar; 2 tsp. dark brown sugar; Pinch of ground cinnamon; 2 Tbsp. chilled unsalted butter, cut into ½ pieces; 1½ cups (195 g) spelt flour; 1 tsp. baking powder; ½ tsp. baking soda; ¼ tsp. ground cinnamon; ¼ tsp. kosher salt; 1 large egg; ⅔ cup (packed; 133 g) dark brown sugar; ⅓ cup vegetable oil; ⅓ cup buttermilk; Zest of 1 lemon; ½ cup (85 g) fresh or frozen blueberries