If using frozen cauliflower, fully defrost the cauliflower and pat dry. You can microwave it for 2 minutes, drain and pat dry.
In a pot or deep fryer, heat oil to 350°F.
In a medium bowl, combine batter ingredients. Toss a few pieces of cauliflower in batter at a time. Add to hot oil and deep fry until golden. Sprinkle with lemon juice and salt. Serve with mayo dipping sauce and/or sweet chili sauce.