The pancakes can be kept warm in a 200 degrees oven.
Whisk together flour, sugar, baking powder, and salt in a bowl. Add eggs, milk, applesauce, and butter; whisk just until combined (batter should be slightly lumpy).
Heat a griddle or cast-iron skillet over medium heat. Brush lightly with butter. Working in batches, pour batter onto griddle 1/2 cup at a time, spacing pancakes 2 inches apart. Cook until bubbles appear on top and edges are slightly dry, 2 to 3 minutes. Flip and cook until golden brown on underside, about 3 minutes more. Repeat with remaining batter, wiping griddle clean and lightly buttering between batches.
Layer sour cream and applesauce between pancakes; serve with more of each on the side.