Gujarti Eggplant and Sweet Potato "Lasagna" with Kadi Sauce

Ingredients:
A Tomato Masala
1 pound sweet potatoes, peeled
1/2 pound eggplant, unpeeled, ends trimmed
3/4 pound zucchini, ends trimmed
1/2 large red bell pepper (4 ounces)
1/2 large green bell pepper (4 ounces)
1/4 cup canola oil
1/2 cup chopped unsalted roasted peanuts
1 teaspoon salt
1 cup gram flour (besan)
3 cups water
1 teaspoon finely chopped fresh ginger
1/2 teaspoon finely chopped fresh Thai green chile
1/2 teaspoon ground turmeric
1 tablespoon whole-milk yogurt
2 teaspoons salt
1/4 teaspoon citric acid powder (see Note)
Cooking spray
Kadi Sauce
for serving

Instructions:
Prepare the tomato masala and set aside.
Prep the vegetables for the filling, keeping all of them separate: •Cut the sweet potatoes into 1/2-inch cubes. •Cut the eggplant into 1/2-inch cubes. •Halve the zucchini crosswise. Stand one of the halves up and cut four 1/2-inch slices of flesh from around the seeds in the center. Dice the flesh into 1/2-inch cubes (discard the seeds. Repeat with the other half. •Cut the bell peppers into 1/2-inch squares.
In a large skillet, heat the oil over medium- high heat until it shimmers. Stir in the sweet potatoes and sauté, stirring occasionally, until parcooked and still a bit crunchy, about 5 minutes. Stir in the eggplant and cook for 4 minutes, stirring frequently. Add the zucchini and cook until the zucchini is soft, about 5 minutes. Add the bell peppers and sauté for 1 minute. Transfer the vegetables to a large bowl. Add the peanuts, tomato masala, and salt and mix well.
Have ready a wide expanse of very clean counter space.
In a medium saucepan, whisk together the gram flour and water until smooth. Add the ginger, green chile, turmeric, yogurt, salt, and citric acid. Cook over medium heat, stirring constantly with a silicone spatula or wooden spoon, until the batter is very thick, 9 to 10 minutes. (It will resemble thick pastry cream or cream puff dough.)
Turn the dough out onto the counter. Working quickly and using an offset spatula, spread it into a very thin (1/8-inch-thick) rectangular sheet roughly 24x20 inches. Use a paring knife to trim the rectangle to an 18-inch square. (Discard the trimmings or snack on them.) Then cut that square into four precise 9-inch squares. The dough cools and sets quickly so you will be able to peel each of the four squares off the counter easily as you need them.
Preheat the oven to 375°F. Grease a 9-inch square baking dish with cooking spray.
Preheat the oven to 375°F. Grease a 9-inch square baking dish with cooking spray.
Spread one-fourth of the vegetable mixture evenly into bottom of the pan, pressing down lightly on it with the back of a spoon so it gets into the corners and is compact rather than loose.
Position one of the lasagna sheets over the vegetables so that it fits exactly in the pan. Repeat with the remaining three portions of vegetables and three lasagna sheets, ending with a lasagna sheet.
Cover the lasagna with a 9-inch square of parchment paper, then cover the dish with foil. Place is on a baking sheet and bake for 40 minutes.
Meanwhile, make (or reheat) the kadi sauce.
To serve, cut the lasagna into six rectangles. Serve in large pasta bowls with kadi sauce ladled over each portion.