Warm the olive oil in a large pot over medium heat.
Soften the onion with a pinch of salt, stirring, about 5–7 minutes.
Stir in the garlic and ginger; cook until fragrant, about 1 minute.
Bloom the garam masala, cumin, coriander, turmeric, and chili powder for 30 seconds.
Cook in the tomato paste, stirring, for another minute to darken slightly.
Pour in crushed tomatoes and vegetable broth; simmer 5 minutes to meld flavors.
Add cauliflower and carrots; cover and simmer until starting to soften, 8 minutes.
Fold in bell pepper, zucchini, and chickpeas; cook uncovered 6–8 minutes, stirring occasionally.
Stir in coconut milk and peas; simmer gently 3–4 minutes until creamy and vegetables are tender.
Season with sugar, pepper, and lemon juice; adjust salt to taste.
Rest 5 minutes off heat, then garnish with cilantro and serve hot.