Preheat the oven to 375°F. Line a 12-cup muffin pan with paper liners.
For the streusel: In a small bowl, mix the flour and sugar. Add the butter and rub it with your fingers until the mixture is crumbly.
For the muffins: Beat the butter and sugar together. Add the eggs, lemon zest, and milk, and mix well. Add the flour, baking powder, baking soda, and salt. Fold in the raspberries.
Scoop the batter into the prepared muffin cups and sprinkle the streusel over the muffins. Bake for about 25 minutes or until golden brown and a toothpick inserted into the center comes out clean. Cool the muffins in the pan for a few minutes before taking them out.
