Boil the water, slowly add the polenta, simmer for approx. 2 mins., stirring constantly. Remove the pan from the heat, mix the rest of the ingredients into the polenta. Put the polenta into the oiled dish and pull upwards to form a small edge.
For the topping
Mix all of the ingredients until smooth, spread across the polenta base.
Spread the asparagus and artichokes (with the cut sides facing upwards) onto the polenta base. Mix together the hazelnuts, salt and olive oil, and spread over the vegetables.
Bake for approx. 25 mins. in the centre of an oven preheated to 180°C.
Mix all of the ingredients together. Serve the salsa separately from the tart.