ceviche is not of Brazilian origin - it seems to have developed all along the Pacific Coast of Central and South America - ceviche is by no means unknown here in Brazil. Contemporary Brazilian chefs have begun to combine ceviche preparation techniques with Brazilian ingredients to create new variations on a traditional theme.
Ceviche is typically made from raw seafood of some sort marinated in lime juice and then flavored with onions, cilantro, and chile peppers. The lime juice "cooks" the fish or seafood rendering it opaque and firm. The dish, served cool or at room temperature, is refreshing and light, and can be presented as a first course, or a light main course.
This recipe, which which has been adapted from a recipe by Chef Felipe Bronze of Rio de Janeiro's Oro Restaurante, combines equal-sized cubes of raw tuna and watermelon to create a checkboard-pattern ceviche. It varies from traditional ceviche in using rice vinegar rather than lime juice to provide the acid that makes ceviche ceviche. This acid is poured over the ceviche at the last minute which allows only the surface of the tuna to "cook", leaving the interior raw - in fact, a take on seared tuna.
Because the fish is served raw, be sure to buy sushi/sashimi-grade tuna. You won't need a lot, so it's best to make sure you have the freshest tuna available. Depending on your preference you can use regular watermelon (which is visually more interesting with its glossy black seeds) or seedless (which is easier to eat).
RECIPE - Tuna and Watermelon Ceviche (Ceviche de Atum e Melancia)
2/3 cup (180 ml) rice wine vinegar
1/4 cup (75 ml) water
1/3 cup (80 gr) granulated sugar
1/2 tsp peel, coarsely chopped fresh ginger
6 oz (160 gr) sushi-grade tuna - ahi or albacore
6 oz (160 gr) watermelon
small red onion, very thinly sliced
1 tsp ancho chile powder (available in Mexican and Latin American markets)
fleur du sel
nigella seeds (optional - available in Indian markets)
Prepare the vinaigrette. In a small saucepan combine the rice wine vinegar, the water, the sugar and ginger. Bring to a boil rapidly over high heat, stirring to dissolve the sugar completely. Remove from heat and let cool to room temperature. Reserve.
Prepare the ceviche. Cut the tuna and the watermelon into equal-sized cubes about 3/4 inch (2 cm) on a side. On each of four plates, place 8 pieces of tuna and 8 pieces of watermelon alternatively to create a checkerboard pattern (see photo). Put two or three thin slices of red onion on top, then sprinkle on fleur to sel to taste, the ancho chile powder and scatter a few nigella seeds over. Carefully spoon equal amounts of vinaigrette over each plate, taking care not to disturb the onion rings. Let stand for 15 minutes to marinate and to allow the flavors to blend. Serve immediately.