Wash the cauliflower and remove any remaining green leaves. Using a sharp knife, cut the head into slices about 2 inches thick.
Peel and finely chop the garlic. In a bowl, mix together the olive oil, salt, pepper, red pepper flakes, sweet paprika, and sugar to create the marinade.
Brush both sides of the cauliflower slices with the marinade and let sit for at least 30 minutes to absorb the flavors.
Grill the cauliflower slices directly on the grill grate or in an aluminum foil pan for about 4 to 5 minutes per side. The steaks should be golden brown and crispy on the outside and tender on the inside. Drizzle with lemon juice before serving.