Preheat your oven to 400°F (200°C).
Grease a muffin tin with cooking spray or line it with muffin liners for easy removal.
In a large mixing bowl, whisk together the all-purpose flour, cornmeal, sugar, baking powder, baking soda, salt, and chopped rosemary until well combined.
In a separate bowl, whisk together the buttermilk, melted butter, canola oil, and eggs until smooth.
Pour the wet ingredients into the bowl of dry ingredients. Gently mix with a spatula until just combined, being careful not to overmix.
Gently fold in the corn kernels and shredded cheddar cheese, ensuring even distribution.
Spoon the batter into the prepared muffin tin, filling each cup about 3/4 full.
Bake in the preheated oven for 18-20 minutes, or until golden brown and a toothpick inserted into the center comes out clean.
Remove the muffins from the oven and let them cool in the tin for about 5 minutes, then transfer to a cooling rack to cool completely.