These muffins are a delicious breakfast or snack that are perfect for on-the-go. The muffins are moist and tender, with a sweet and tangy strawberry and rhubarb filling. To make the muffins, mix together flour, sugar, baking powder, and salt. Add in melted butter, milk, and eggs, and mix until smooth. Fold in the strawberry and rhubarb filling and spoon the batter into muffin cups. Bake until golden brown and enjoy warm or at room temperature.