Cooking Indian dishes at home doesn’t have to require hours of simmering or a long list of ingredients. Precooked lentils cut that time by more than half, as does a slurry (a mixture of stock and flour or cornstarch) for thickening the stew. Unsalted ketchup is the unexpected secret ingredient that brings the dish together, with just enough sweetness, vinegar tang, and tomato acidity to balance the dish. Serve with whole-grain naan (such as Stonefire), brushed with oil and warmed at 350°F for 10 minutes or grilled for 1 to 2 minutes on each side.
Heat oil in a large saucepan over medium-high. Add onion; sauté 4 minutes. Add zucchini and garlic; cook 3 minutes. Add tomato, curry powder, and ketchup; cook 1 minute, stirring constantly.
Combine stock and flour in a small bowl. Add stock mixture to pan; bring to a boil. Stir in salt and lentils; cook 3 minutes. Remove pan from heat; stir in lime juice. Divide lentil mixture among 4 bowls; top evenly with yogurt and cilantro.