Preheat oven to 350 degrees F. Line a muffin pan with paper or silicone liners and set aside.In a small bowl, whisk together the flour, baking soda, salt, and lemon zest.In a large bowl fitted with an electric whisk (or beaters), cream the butter until smooth.Turn the speed down to low and slowly add in the egg, syrup, milk and vanilla.With the speed still on low slowly add in the flour, scraping the sides of the bowl if necessary.Carefully fold in the raspberries with a spatula until well combined.Use a small ice cream scooper or large spoon to add the batter to the muffin cups. Bake until a toothpick comes cleans when inserted in the center, about 18 to 20 minutes.