Preheat oven to 375 degrees. Place paper liners into the cups of a 12 count muffin pan.
In a large mixing bowl and with an electric mixer at medium speed, cream butter and sugar together until light and fluffy; 2-3 minutes. Beat in egg, vanilla, and the zest and juice of one lemon. Beat in milk.
In a medium size bowl mixing bowl, combine flour, baking powder and salt. Gently mix into the wet ingredients until just combined. Gently fold in the raspberries.
Fill paper-lined muffin cups three-fourths full. *Note - if you don't want to use paper liners, be sure to grease the muffin pan really well.
In a small bowl, combine brown sugar, flour and 2 teaspoons lemon zest. Cut in butter with fork or pastry cutter until crumbly. Sprinkle over each muffin.
Bake muffins in the preheated oven for about 25 minutes, or until a toothpick inserted in muffin comes out clean.
Cool in the pan for 10 minutes, then transfer to a cooling rack.