1. For the dough: Whisk the flours, baking powder, and salt together in a large bowl. Add the melted butter and 2 ½ cups of warm water and stir until a shaggy mass forms. You may need to add up to ½ cup additional water. The goal is a soft, pliable dough that isn’t too sticky. Transfer to a floured work surface and knead until smooth, about 5 minutes. Form the dough into a ball, rub with a little oil, wrap in plastic wrap, and set aside to rest for about 1 hour. (Another option is to use a stand mixer. Use the paddle attachment for the initial mixing, then switch to the dough hook for the 5 minutes of kneading.) Make the filling while the dough rests.

2. For the filling: Heat 1 tablespoon oil in a large saucepan over medium-high heat. Add the onion, garlic, and 1 teaspoon salt and sauté until the onion is translucent, about 2 minutes. Add the split peas and 6 cups water. Bring to a boil, then reduce the heat and simmer until the peas are easily crushed between your fingers—tender enough to eat but not turning into soup, about 25 minutes.

3. Drain the peas and transfer them to a food processor. Add the remaining 2 tablespoons oil, the turmeric, cumin, a pinch of cayenne, and the remaining 1 teaspoon of salt. Pulse until the peas are coarsely pureed, retaining a bit of texture. Taste and adjust seasoning. You may also need to add a couple tablespoons of water. The right texture is one that is stiff enough to form a ball, without being bone-dry. If it is too wet, it will make the roti soggy.

4. When the dough is done with its initial rest, divide it into 12 pieces (if using a scale, they will be about 135 grams each). Form into balls, place on a lightly floured board or baking sheet, cover with plastic wrap, and allow to rest for an additional 30 minutes.

5. To cook the breads: Heat a large, heavy skillet (at least 12 inches in diameter) or griddle over medium heat. Take one ball of dough and, on a lightly floured work surface or a silicone board, roll it out to a 5-inch circle. Place 3 tablespoons of the filling in the center. Pull the edges of dough up around the filling toward the center and pinch to seal completely. Flatten with your hand and then roll out to a 10-inch circle less than ¼ inch thick. (You can start cooking the bread while continuing to form the rest of the breads.)

6. Melt a little butter in the skillet and put in the first bread. Cook until lightly browned on the first side, about 1 1/2 minutes, pushing down on the edges occasionally. You don’t want it to brown so much that it is crispy; the bread should remain soft. Turn and cook the other side until lightly browned, about 1 1/2 minutes more. Repeat with remaining breads, stacking them on a plate and covering them to keep them warm. Serve immediately or reheat if made in advance.