Place lemon juice in a large liquid measuring cup and add enough milk to make two cups. Mix well, then let stand for five minutes. Place eggs in a blender and process on medium speed for a few seconds. Add lemon-milk mixture and melted butter to the beaten eggs and process until well mixed, about 5 seconds. In a medium bowl, wisk together the flour, sugar, salt, baking soda and baking powder. Add dry ingredients to wet ingredients in the blender and pulse a few times in short burst on medium speed, stop and scrape down sides of blender as necessary, then continue to process on medium speed until just blended and no lumps of flour remain, another 10 to 15 seconds (blend everything together for only the shortest time necessary). Heat a heavy skillet or griddle over medium-high heat, or if using an electric griddle, heat to 375 degrees F. Skillet is ready when a few drops of water flicked onto the hot surface forms beads and dances across it. When hot, lightly grease the skillet with bacon grease, vegetable oil, or spray with nonstick cooking spray, and adjust heat to maintain temperature. Pour batter from blender, in about 1/4 to 1/3 cup amounts, onto hot skillet to form 5-inch pancakes, making sure to leave space between them. Cook until batter has set, tops have bubbled, and bottoms are golden brown, about 1 1/2 to 2 minutes. Flip pancakes and cook until golden brown on second side, about 30 seconds to 1 minutes more. Repeat with remaining batter, adding more grease or oil to skillet as necessary. Serve immediately, or to keep warm until all pancakes are cooked; place pancakes side-by-side, uncovered, on a wire rack (sprayed with nonstick cooking spray) set over a baking pan in a 200-degree F oven. Serve topped with butter and drizzled with either a warm maple or fruit syrup. Cooks Notes: - You can substitute 2 cups of buttermilk for the lemon-milk mixture, if desired. - If the tops of the pancakes bubble and the bottoms don't brown, the heat is too low; if the bottoms brown before the tops bubble, the heat is too high.