Soak the chickpeas: Rinse and sort through the chickpeas. Place them in a large container and cover with about 1 quart of water. Cover and refrigerate overnight or up to 24 hours.
Prepare the mixture: Drain the chickpeas well. Add them to a food processor with the onion, garlic, parsley, and cilantro. Pulse until the mixture resembles breadcrumbs: fairly fine, but not a paste. Stop and scrape down the sides as needed.
Add seasonings and oil: Add salt, pepper, cumin, coriander, cayenne, cardamom, chickpea flour, and 1 tablespoon olive oil. Blend again briefly, just until everything is evenly combined. Do not over-process.
Chill the mixture: Transfer to a bowl, cover, and refrigerate for 30 minutes.
Preheat the oven: Cut a piece of parchment paper to fit your baking sheet and set it aside. Place the baking sheet (without the parchment) in the oven and preheat to 400°F.
Add baking powder: Once chilled, mix the baking powder into the falafel mixture.
Shape the falafel: Scoop about 2 tablespoons of the mixture per falafel, roll into balls or patties, and flatten to about ½ inch thick. Place them on a cutting board and brush the tops with 1 tablespoon of olive oil.
Prepare the baking sheet: Carefully remove the hot sheet pan from the oven. Place the parchment paper on top and brush with 1 tablespoon olive oil.
Bake: Using a spatula, gently transfer the falafel to the baking sheet. Bake for 20 to 24 minutes, flipping halfway through, until golden brown on both sides.