Prepare the tofu: If you haven't already, press the extra-firm tofu for at least 30 minutes to remove excess water. Cut the pressed tofu into uniform 1-inch cubes.

Whisk together the marinade: In a medium bowl, combine the olive oil, lemon juice, minced garlic, smoked paprika, cumin, coriander, turmeric, cayenne pepper (if using), salt, and black pepper. Whisk until thoroughly emulsified.

Marinate the tofu: Add the tofu cubes to the marinade mixture. Gently toss to ensure all pieces are evenly coated. Cover and refrigerate for at least 20 minutes, or up to 4 hours for maximum flavor absorption.

Assemble the kebabs: Thread the marinated tofu alternately with chunks of red onion, green bell pepper, and cherry tomatoes onto metal or pre-soaked wooden skewers.

Cook the kebabs (Grill Method): Preheat your grill to medium-high heat (about 400°F or 200°C). Lightly oil the grates. Place the skewers on the grill and cook for 4-5 minutes per side, rotating until the tofu is nicely browned and the vegetables are tender-crisp (about 16-20 minutes total).

Cook the kebabs (Oven/Broiler Method): Preheat the oven to 400°F (200°C). Line a baking sheet with parchment paper. Arrange the skewers on the sheet and bake for 18-22 minutes, flipping halfway through, until golden brown.

Serve immediately, perhaps drizzled with extra lemon juice or served alongside hummus and pita bread.