Apple-Buckwheat Pancakes

In a large bowl, whisk together flours, sugar, baking powder, baking soda, and salt until very well combined, about 30 seconds. In a large measuring cup, beat together buttermilk, lemon juice, eggs, and butter. Make a well in dry ingredients; stir in wet mixture until lumpy and just combined. Let rest 10 minutes.

Preheat oven to 200 degrees and place a rimmed baking sheet fitted with a wire rack inside. Heat a large nonstick or cast-iron skillet over medium; add oil, then wipe with a paper towel, leaving behind a thin film.

Working in batches, add heaping quarter-cups of batter to skillet, spreading lightly with the bottom of the cup. Cook, adding apple slices to each pancake as bubbles form, until edges have set and undersides are golden-brown, 2 to 3 minutes. Sprinkle with sugar, then flip and cook 2 minutes more. Transfer finished pancakes to oven to keep warm. Serve with Greek yogurt and maple syrup.