Cream butter and sugar in a large bowl until light and fluffy. Add egg vanilla, and the zest and juice from your lemon. Mix well. Beat in milk.
In a second bowl, combine flour, baking powder and salt. Gently mix the wet and dry ingredients until just combined. Fold in the raspberries.
Pour batter into a prepared muffin tin, filling each well about ¾ full.
In a small bowl, combine brown sugar, flour and additional lemon zest, if desired.
Cut in butter with a fork, pastry cutter, or your electric mixer, until crumbly. Spoon streusel on top of the batter for each muffin.
Bake 25 minutes in a 375° F oven, or until a toothpick inserted into the middle of a muffin comes out clean.
Calories are automatically generated. For best results calculate based on your exact ingredients.To create a dome topped muffin (bakery style!): Start your muffins at 400F for the first 6 - 8 minutes, and then lower it to the normal cook temp until baked through. Want a more intense raspberry flavor throughout muffin? Smash half the berries before adding them to the batter!