Step 1: Preheat the Oven. Begin by preheating your oven to 350°F (175°C).
Step 2: Prepare the Muffin Tin. Grease a muffin tin with non-stick spray or line it with paper liners.
Step 3: Mix the Dry Ingredients. In a large mixing bowl, whisk together the gluten-free flour, brown sugar, baking powder, baking soda, ground cinnamon, and kosher salt until well combined.
Step 4: Combine the Wet Ingredients. In another bowl, whisk together the milk, canola oil, eggs, and vanilla extract until smooth.
Step 5: Bring It Together. Pour the wet ingredients into the dry ingredients and gently fold until just combined.
Step 6: Prepare the Topping. In a small bowl, combine the gluten-free flour, brown sugar, cinnamon, kosher salt, and softened butter. Mix until crumbly.
Step 7: Fill the Muffin Tin. Spoon the muffin batter into the prepared muffin tin, filling each cup about ¾ full. Sprinkle the topping mixture over each muffin.
Step 8: Bake. Bake for 18-20 minutes, or until a toothpick comes out clean.
Step 9: Cool. Allow the muffins to cool in the tin for 5 minutes before transferring them to a cooling rack.