Preheat your oven to 375°F (190°C). Line a 12-cup muffin tin with paper liners or lightly grease each cup.
Mix the dry ingredients in a large bowl: flour, masa harina, sugar, salt, baking soda, and baking powder.
In a separate bowl, whisk together the buttermilk (or yogurt + milk), egg, vanilla extract, and melted butter.
Pour the wet ingredients into the dry and stir gently until just combined. The batter should be thick but spoonable. If needed, add a splash of milk to reach a muffin-like consistency.
Fold in the shredded cheese until evenly distributed throughout the batter.
Fill the muffin cups about ¾ full. Optional: sprinkle a bit of cheese on top for extra flavor and color.
Bake for 18–22 minutes, or until the tops are golden and a toothpick inserted into the center comes out clean.
Cool for a few minutes in the pan, then transfer to a wire rack. Serve warm with butter or alongside your favorite chili (link in blog!).