In a medium-sized mixing bowl, combine the flour, sugar, baking powder, baking soda, and salt and whisk well.
In a large measuring cup, combine the eggs, buttermilk, melted butter, lemon juice, lemon zest, poppy seeds, and vanilla extract and whisk to break up the eggs.
Add the wet ingredients to the dry ingredients and gently fold them together, just until combined. The batter should still be a little lumpy. Set aside.
Heat a pan or nonstick griddle over medium heat, then add about 1 tablespoon of butter to grease the pan. For each pancake, pour about 1/3 cup batter onto the hot griddle and let it spread out into a 4" round pancake.
Allow the pancakes to cook until bubbles appear on the surface and the edges are beginning to look cooked, or about 2 minutes. Flip the pancakes, using a spatula, and continue to cook the other side until golden and cooked through, or about 1 minute more.
Repeat this process with remaining batter. Serve pancakes with butter, syrup, or your favorite toppings. Enjoy!