Marshe Bieu — "old market" in Papiamentu — is the best lunch spot in central Willemstad. The covered market hall in Punda has a row of cook stalls run by local women, serving traditional Curaçaoan food at very low prices: stoba, Kadushi soup, goat stew, grilled fish, and funchi. The stalls have been in operation for generations; some of the recipes have been passed down for decades.
This is where government workers and local shopkeepers eat, not where tourists are directed. Arrive between 11am and 1pm for the freshest food and the most activity. Point at what looks good; the cooks will explain everything if you ask. Cash only, very cheap.