Preheat your oven to 350°F (175°C) and line a muffin tin with paper liners or grease it lightly.
In a large bowl, whisk together the flour, baking powder, baking soda, salt, granulated sugar, brown sugar, and cinnamon (if using).
In another bowl, mix the Greek yogurt, vegetable oil, eggs, and vanilla extract until well combined.
Pour the wet ingredients into the dry ingredients and stir gently until just combined. Do not overmix.
Fold in the chopped rhubarb until evenly distributed throughout the batter.
Spoon the batter into the prepared muffin tin, filling each cup about 2/3 full.
Bake for 18-22 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
Allow the muffins to cool in the tin for 5 minutes before transferring them to a wire rack to cool completely.