1. Preheat your oven to 375 F (190 C). Line a 12-cup muffin tin with paper liners or lightly grease each cup with cooking spray.

2. In a large mixing bowl, whisk together the unfed sourdough starter, milk, eggs, and olive oil (or melted butter) until well combined and smooth.

3. In a separate medium bowl, combine the gluten-free all-purpose flour blend, baking powder, baking soda, salt, and black pepper. Whisk these dry ingredients together thoroughly.

4. Pour the dry ingredient mixture into the wet ingredient mixture. Stir gently with a spatula or wooden spoon until just combined. Do not overmix.

5. Gently fold in the cooked quinoa, shredded cheese, chopped chives (or green onions), and diced bell pepper into the batter. Mix just until these additions are evenly distributed.

6. Divide the batter evenly among the 12 prepared muffin cups, filling each cup about two-thirds full.

7. Bake for 20-25 minutes, or until the muffins are golden brown on top and a wooden skewer or toothpick inserted into the center comes out clean.

8. Remove the muffin tin from the oven and let the muffins cool in the tin for 5 minutes before transferring them to a wire rack to cool completely. Enjoy warm or at room temperature.