Using a mixer, cream together the softened butter and the sugar.
Add milk and mix on low speed.
Add the flour 1/2 cup at a time and mix. Scrape down the sides of the bowl to make sure that it is all getting mixed into the batter.
Add egg, lemon extract, salt, baking powder and mix.
Using a spoon or a spatula, hand stir the berries into the batter. Since raspberries are fairly soft, they will mash a bit, but that's ok. Hand mixing them into the batter still gives you nice, big chunks of berries in the batter which is what we want.
Line a muffin tin with muffin liners. This recipe makes 8 large muffins or 11-12 smaller muffins.
Scoop batter into each tin.
If you are making larger muffins, fill the unused cups in the muffin tin about 1/3 of the way with water. This will help the muffins bake evenly.
Bake at 375 for 18-21 minutes or until muffins are cooked though the center.
Cool on a baking rack before serving.
Notes
Store in an airtight container for up to 4 days. They will get more and more moist the longer you store them, so you could line the container with a paper towel if you prefer.These muffins will last up to three months in the freezer. Store them in a ziplock bag and try to get as much air out of it as possible before you seal it. When you are ready to eat them, simply leave them out on the counter to come to room temperate, and then reheat in the microwave for a few seconds.