Heat the oil, sauté the onion and garlic for approx. 5 mins., place in a tall container and allow to cool a little. Using a melon baller, scoop 12 balls out of the melon, cover and chill to use as a garnish. Cut the remaining melon into chunks (yields approx. 150 g), add to the onions along with the tomatoes. Pour in the stock, puree, strain, season and chill for approx. 1 hr. Plate up the chilled soup, garnish with melon balls, basil and spelt crackers.