Guasacaca is often served over Venezuelan cornmeal cakes called arepas.
Arepas are round, usually griddled or baked cakes made from ground maize dough. They are a major food in Venezuela and Colombia, and they can be split open and filled or served alongside other foods. In Venezuelan cooking, guasacaca is used as a sauce over arepas as well as over grilled meats, empanadas, and other dishes.
The pairing works because the arepa’s relatively neutral, toasted corn flavor provides a sturdy base for the sauce’s acidity, herbs, oil, and—when included—avocado. Guasacaca may be blended smooth or prepared with a chunkier texture, so it can function as either a topping or a dipping sauce.
Pupusas are also stuffed corn cakes, but they are especially associated with El Salvador. Tostones are twice-fried green plantains, while tamales are steamed preparations made from masa or other doughs and wrapped in leaves or husks. Those foods can be eaten with sauces, but they are not the Venezuelan cornmeal cakes named in the question.