Preheat the oven to 375°F (190°C). Line a muffin pan with paper liners or grease well.
Mix the dry ingredients in a large bowl: flour, baking powder, and salt. Set aside.
Whisk the wet ingredients in a separate bowl: melted butter, sugar, eggs, sourdough discard, milk, and vanilla until smooth.
Combine wet and dry ingredients. Stir gently with a wooden spoon until just combined—don’t overmix
Fold in strawberries until evenly distributed.
Fill muffin cups about ¾ full. Sprinkle tops with sugar if desired.
Bake for 20–25 minutes, or until lightly golden and a toothpick inserted in the center comes out clean.
Cool for a few minutes, then transfer to a cooling rack. Enjoy warm or store in an airtight container.