01 - Preheat the oven to 375°F. Line a 12-cup muffin tin with paper liners or lightly grease with cooking spray.
02 - In a large mixing bowl, whisk together flour, sugar, baking powder, baking soda, and salt until evenly distributed.
03 - In a separate bowl, whisk eggs, oil, milk, and vanilla extract until fully combined and smooth.
04 - Pour the wet mixture into the dry ingredients. Mix gently with a spatula until just combined—do not overmix as this will result in tough muffins.
05 - Gently fold in the diced strawberries and rhubarb until evenly distributed throughout the batter.
06 - Divide the batter evenly among the 12 muffin cups, filling each about three-quarters full. Sprinkle tops with coarse sugar if desired for a crunchy topping.
07 - Bake for 20 to 22 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
08 - Let muffins cool in the tin for 5 minutes, then carefully transfer to a wire rack to cool completely.