Adjust oven rack to middle position and preheat oven to 350°. Line the cups of a muffin tin with 12 paper liners. Set aside.
Combine flour, sugar, baking powder, soda, and salt in a mixing bowl. Stir well; set aside.
Using metal blade in food processor, process cream cheese, lemon juice, and vanilla in food processor until smooth.
Add eggs and process 15 seconds. Scrape down side of container with a spatula.
With processor running, pour hot melted butter through food chute gradually, but within 10 seconds.
Process another 10 seconds.
Add milk and process 5 seconds.
Add dry ingredients to container and mix with 4 to 6 half-second pulses.
Add blueberries and fold in with a spoon.
Pour an equal amount of batter into each muffin cup, filling each about 2/3 to 3/4 full.
Bake in preheated 350° oven for 30 minutes. Cool on rack 15 minutes.
Makes 12 muffins.