Preheat the oven to 400°F. Lightly spray a standard 12-cup muffin tin with baking spray then place a paper muffin cup in each cavity. Set aside.
Use your hands or a knife to section the cream cheese into small chunks. Set aside.
Have one medium and one large mixing bowl ready. Wash the lemon and then use a citrus zester or Microplane to finely grate all of the zest into the medium bowl. Slice the lemon in half and squeeze out as much juice as you can into the large mixing bowl (approximately ¼ cup).
Add the flour, sugar, baking powder, baking soda, and salt to the medium-sized bowl with the lemon zest. Whisk well to combine and set aside.
Add the vegetable oil, eggs, milk, and vanilla to the bowl with the lemon juice. Whisk well to combine.
Add the dry flour mixture to the bowl of wet ingredients. Gently stir the mixture until it’s about halfway mixed. Add the frozen raspberries and cream cheese chunks. Continue to stir until the berries and cream cheese are well distributed and the flour is just mixed in.
Spoon the muffin batter evenly between the 12 prepared muffin cups. Top each muffin with a sprinkle of coarse sugar if using.
Place the muffin tin in the oven and bake for 10 minutes, then reduce the heat to 350°F and bake for 14 to 16 minutes more. Transfer the muffin tin to a wire rack and cool the muffins for 10 minutes. Remove the muffins from the tin and place them directly on the rack to cool completely.