Preheat your oven to 375°F (190°C) and line a muffin tin with paper liners.
In a large mixing bowl, combine the flour, granulated sugar, brown sugar, baking powder, baking soda, and salt.
In another bowl, whisk the egg, then add milk, vegetable oil, and vanilla extract. Mix well.
Pour the wet ingredients into the dry ingredients. Stir gently until just combined.
Fold in the diced strawberries carefully to avoid mashing them.
Fill each muffin liner about two-thirds full with the batter.
Bake in the preheated oven for 20-25 minutes or until a toothpick inserted in the center comes out clean.
Remove from the oven and let the muffins cool in the tin for 5 minutes.
Transfer muffins to a wire rack to cool completely.
Enjoy warm or store for later!