Wrap the block of tofu in paper towels and place in a wide bowl with a heavy weight to squeeze out the water content. This may take 1-2 hours. (Note: Placing something heavy on the wrapped tofu block will help to release the water that's stored inside. You may have to unwrap the tofu, squeeze the water out of the paper towels and rewrap the tofu occasionally to make sure the maximum amount of water is released.)
Once all the water has been strained from the block of tofu, cut it into approximately 1/2 inch cubes.
Mix all the spices, salt and greek yogurt in a bowl.
Add the cubed tofu, bell peppers, onions and cauliflower and mix well. (Note: The veggies listed in the ingredients are suggestions. You can also add other veggies such as zucchini, mushrooms, celery, broccoli, etc.)
Allow this to marinate for about 2 hours for the flavors to really incorporate.
Wet the skewer sticks. Feed the cubes of tofu, bell peppers, onions, and cauliflower onto the sticks one at a time and set aside.
Cook on a grill at about 400F for about 15 minutes, turning halfway. (Note 3: We laid the skewers onto a grilling mat. You can also make a batch without skewers. Simply spoon the veggies with the masala gravy onto the grilling mat.)