01 - Preheat the oven to 350°F. Line a standard 12-cup muffin tin with paper liners, or lightly grease each well with butter or oil.
02 - In a large bowl, whisk together the ricotta cheese, whole milk, vegetable oil, eggs, vanilla extract, lemon zest, and lemon juice until the mixture is smooth and homogeneous.
03 - In a separate medium bowl, whisk together the all-purpose flour, granulated sugar, baking powder, baking soda, and salt until evenly distributed.
04 - Pour the dry ingredient mixture into the wet ingredient mixture. Stir gently with a spatula until just combined — a few small lumps are fine. Do not overmix, as this will produce tough muffins.
05 - Gently fold the raspberries into the batter using a spatula, taking care not to crush them and streak the batter with their juices.
06 - Divide the batter evenly among the prepared muffin cups, filling each about three-quarters full. If desired, sprinkle the tops with coarse sugar for a crisp, crunchy finish.
07 - Bake for 20 to 24 minutes, or until the tops are golden and a toothpick inserted into the center of a muffin comes out clean.
08 - Let the muffins cool in the pan for 5 minutes, then transfer them to a wire rack to cool completely.