Grease or line a 12-cup muffin tin with muffin liners.
In a large bowl, whisk together the 3 cups gluten free flour, 2 teaspoons baking powder, ¼ teaspoon baking soda, 1 teaspoon cinnamon and 1 teaspoon fine sea salt.
In a medium bowl, whisk together the 1 cup sugar, 1 cup buttermilk, ½ cup oil, and 2 large eggs until completely combined. Pour into the dry ingredients and gently mix until combined. Fold in the 1 ½ cups strawberries until just incorporated.
Preheat the oven to 375℉. Divide the batter evenly between the muffin cups. Let the batter rest while the oven heats.
Place the muffin tin in the oven and bake for about 20 minutes, until a tester inserted in a muffin comes out clean. Let the muffins cool for 5 minutes in the tin and then turn them out onto a wire rack to cool completely.
Notes
Use ripe, firm strawberries. Choose strawberries that are ripe, but not soft. This is so that they hold their shape during baking and don’t release too much moisture.
Chop the berries. I like to chop my strawberries into smallish pieces (about the size of blueberries) for even distribution throughout the batter.
Don’t overmix. Stir the batter just until combined to keep the muffins tender. And when adding the strawberries, fold them in gently so that they don't disintegrate.
Rest the batter. All gluten-free batters benefit from a rest before baking to allow the gluten-free flour to hydrate (this prevents dryness/grittiness). Let the batter rest in the muffin tin for 10-20 minutes (or while the oven heats) before baking.
Use muffin liners. I generously grease the muffin tin and have no problem releasing the muffins, but if you're concerned about sticking, use parchment or silicone muffin liners.
Buttermilk substitute: Mix 1 cup of whole milk with 1 tablespoon of lemon juice or vinegar, let it stand for 10 minutes, then add it to the batter instead of buttermilk.
Make it dairy-free. To make these muffins dairy-free, add 1 tablespoon of vinegar to 1 cup of non-dairy milk. Let the mixture stand for 10 minutes, then use it in the recipe.
Citrus zest. Rub in the zest of 1 lemon into the sugar to release its oils, then proceed with the recipe.