In a large batter bowl, whisk together the flour, sugar, baking soda, baking powder, and salt.
In a separate bowl or 1-quart liquid measuring cup, whisk together the buttermilk, egg, egg yolk, lemon zest and juice, and melted butter.
Pour the liquid mixture into the large bowl with the dry ingredients. Using a rubber spatula, mix just enough for the dry ingredients to be wet - there should still be a lot of lumps (you want those lumps for fluffy buttermilk pancakes). Let the batter rest for about 10 minutes.
Heat a griddle, skillet or large pan to between medium and medium-low heat or 350°F for an electric griddle. After heated for several minutes, add oil to coat the pan.
Use a 1/3 cup or 1/2 cup measuring cup to scoop batter and pour onto the griddle (they will be roughly 5-7 inches depending on the cup size - go up to 2/3 cup for 4 extra large pancakes). Repeat, leaving space between the pancakes.
Cook until edges are set, top has bubbles, and underside is a golden brown - 2 to 3 minutes. Flip and cook another 1-2 minutes until other side is also golden brown.
Transfer to a plate or a baking sheet*. Repeat using remaining batter.
*You can keep pancakes warm in an oven preheated to 200°F while you cook up the remaining pancakes.
Source: ATK Kids