Heat oven to 350°F (180°C) and line a 7 x 3 inch (17 x 7 cm) loaf pan with parchment paper. This prevents sticking and helps the bread come out easily after baking.
Rinse the lentils under cold water, then add them to a small pot and cover completely with water. Bring to a boil, reduce heat and cook until the lentils are completely soft. You don’t need to soak them beforehand; just cook until they easily mash.
Drain any excess water, then transfer the lentils to a blender along with egg, Greek yogurt, baking powder and seasonings. As an alternative you can combine everything in a bowl and blend with a hand mixer.
Blend until you get a thick, smooth puree with no chunks left.
Add the lentil batter to a bowl and mix in the chickpea flour, starting with a small amount and adding more as needed. You want a thick, spreadable batter that holds its shape in the pan. If your lentils were very moist, you’ll likely need the full amount.
Pour the batter into the prepared pan, then smooth the top with the back of a spoon so it bakes evenly. You can sprinkle extra herbs, a pinch of salt, oat flakes or seeds on top if you'd like a more flavorful crust.
Bake in the hot oven until the lentil loaf is firm, golden and set in the center. Let the bread cool in the pan for a few minutes before lifting it out to cool fully on a rack.