Preheat griddle to 350°F, or a nonstick pan to medium-high heat. Whisk together the butter, eggs, buttermilk, sour cream, lemon juice, and zest in a large bowl. Add the flour, sugar, baking powder, soda, and salt all at once, and mix together until just incorporated- do not overmix.
Butter the griddle/pan once hot. Drop batter onto the griddle/pan in ⅓ cup quantities, using the back of the measuring cup to slightly spread out the thick batter, until the pancake batter is about 6 inches in diameter. Cook until some holes have formed on top of the uncooked side and the bottom is golden brown. Flip the pancakes and cook until golden brown on both the top and bottom.
Buttermilk Syrup
In a medium-sized saucepan, heat the butter, sugar, and buttermilk over medium-high heat, whisking as the mixture comes to a soft boil. Cook for one minute, still whisking regularly, and remove from heat. Whisk in vanilla and baking soda. Serve with hot pancakes.