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 the flour, sugar, baking powder, baking soda, and salt until evenly blended.
03 - In a separate bowl, whisk the 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 just until combined; avoid overmixing to keep muffins tender.
05 - Gently fold the diced strawberries and rhubarb into the batter until evenly distributed.
06 - Divide the batter evenly among the 12 muffin cups. Sprinkle the tops with coarse sugar if using.
07 - Bake for 20–22 minutes, or until a toothpick inserted into the center comes out clean and the tops are golden brown.
08 - Let the muffins cool in the tin for 5 minutes, then transfer to a wire rack to cool completely before serving.