Chickpea Flatbread With Chaat Masala Tomatoes

Preparation

1. Start the flatbread: 

   1. Step 1

      Add the chickpea flour to a large bowl, then add the lukewarm water in stages, whisking as you go (this prevents lumps). Whisk in 10 grinds (about a scant half teaspoon) of black pepper and 1¾ teaspoons kosher salt (or half that, if using table or sea salt) until smooth. Cover and let rest at room temperature for at least 1 hour or up to 4 hours (a slightly funky smell is normal).

   2. Step 2

      Shortly before baking, heat the oven to 450 degrees with a rack in the center. Line a rimmed sheet pan (18-by-13 inches) with parchment paper, leaving a small overhang.

2. Make the tadka:

   1. Step 3

      Set a fine-mesh sieve over a heat-proof medium bowl. Heat the oil in a small saucepan over medium-low until it reaches 325 degrees, 3 to 5 minutes (the oil is ready if a piece of minced garlic dropped into the oil sizzles immediately). Once the oil is hot, add the mustard seeds, swirling the pan frequently. Once they start to pop, add the cumin seeds and continue swirling until the cumin darkens a few shades, 10 to 15 seconds. Immediately pour through the sieve, reserving both the oil and the spices.

   2. Step 4

      Pour the infused oil onto the lined sheet pan and spread it across the bottom and up the sides with a pastry brush or spatula.

3. Bake the flatbread:

   1. Step 5

      Whisk the batter again to smooth out any lumps. Working near the stove to minimize spilling, pour the batter evenly into the oiled pan. Use a spoon to incorporate the oil into the batter (some streaks are fine). Scatter the reserved spices over the top and stir them in with the spoon to distribute.

   2. Step 6

      Bake for 12 minutes, then rotate the pan 180 degrees and bake until the edges are golden brown and the center is set, about 10 minutes more (check 2 minutes early if your oven runs hot).

4. While the flatbread bakes, prepare the yogurt sauce and the tomato salad.

   1. Step 7

      Make the yogurt sauce: In a bowl, stir together the yogurt, 2 teaspoons lime juice, a pinch or two of salt and a few grinds of pepper. Finely grate the garlic into the yogurt and mix well. Taste and adjust with more salt or lime juice. Refrigerate until ready to serve.

   2. Step 8

      Make the tomato salad: Dice the tomatoes and add to a medium bowl. Thinly slice the onion (you should have about ¼ cup/75 grams), chop the cilantro and finely chop the serrano chile, if using, and add all to the bowl. Add ¼ teaspoon salt, a few grinds of pepper, the chaat masala and 2 teaspoons lime juice. Mix, then taste and add more salt, lime or chaat masala as desired.

   3. Step 9

      When the flatbread is done baking, transfer the pan to a wire rack and cool for 5 minutes. Use the parchment to transfer the flatbread to a cutting board and slice it into squares. To serve, instruct eaters to spread a thin layer of yogurt sauce on each square and top with a spoonful of tomato salad.