Preheat the oven to 220°C (425°F/Gas 7). Grease a high-sided ovenproof dish, ovenproof frying pan (skillet) or high-sided baking tray and pop it in the oven until it's stinking hot.
Place the polenta, salt, sugar, baking powder, spices, chilli flakes and paprika in a bowl and mix to combine.
Make a herb oil by whizzing the oil with the coriander and garlic in a mini-chopper or pounding together in a pestle and mortar.
In a separate bowl, whisk together the melted butter, milk, herb oil, lime juice and egg. Pour the liquid ingredients into the polenta mixture and stir. Fold through the cubed avocado, diced red onion and tomato.
Remove the hot dish from the oven and pour the mixture in, topping it with the sliced avocado and sliced red onion.
Turn the oven temperature down to 200°C (400°F/Gas 6) and bake for 20-25 minutes, until puffed and golden. Remove from the oven and leave to cool. Fry 4-6 eggs and serve with the bread.