For the sweet onion dip: preheat oven to 190°C.
Peel onion and cut in quarters, leaving stem end intact. Place onion in a baking dish, brush with oil, sprinkle with brown sugar or brush with maple syrup and bake, uncovered, for 30 to 40 minutes, until soft and caramelized on the surface. Let cool.
Cut off stem-end of onion and purée in food processor. Add goat cheese and feta and pulse until smooth. Add sour cream and season to taste.
Chill until ready to serve. This dip can also be served warm. To heat, spoon dip into a baking/serving dish and heat at 175°C for 12 to 15 minutes.
For the veggies, arrange prepared vegetables on a serving platter and serve with dip.
To prepare and store veggies in advance, arrange on platter, cover with damp paper towel, then cover loosely in cling film.