In a large bowl, combine yogurt, lemon juice, ginger, oil, garlic, salt, garam masala, turmeric, paprika and cayenne. Whisk until smooth. Set aside.
Bring a large pot of lightly salted water to a boil. Add broccoli and cauliflower; simmer for 2 minutes. Drain and run under cold water. Pat dry.
Add broccoli, cauliflower, tomato and onion to yogurt mixture; stir gently to coat. Cover and refrigerate for 30 minutes.
Heat a gas grill to mediumhigh or the coals in a charcoal grill to medium-hot. Lightly grease grates. Alternately thread broccoli, cauliflower, tomato wedges and onion onto wood skewers. Grill for about 2 to 3 minutes per side, until lightly charred. Remove to a serving platter.
Serve with Mint Raita and, if desired, grilled naan.
In a small bowl, combine 1 cup plain Greek yogurt, 1/4 peeled seedless cucumber, shredded, 3 tbsp chopped fresh mint, 1 tsp lemon juice and 1/8 tsp salt. Cover and refrigerate until serving.
