A last-minute get-together requires a main dish that doesn't need to be marinated. Serve this impressive salmon, glazed with a Cuban-inspired green sauce made with cilantro, jalapeño, and citrus that cooks on the grill in 15 minutes.
Heat a skillet over medium. Add garlic and sunflower and cumin seeds; cook, shaking skillet frequently, until garlic is golden in places and cumin is fragrant, about 2 minutes. Transfer to a food processor; add citrus zests and juices, cilantro, jalapeño, and 1 teaspoon salt. Pulse until mixture has texture of a loose paste. Add oil and 2 tablespoons water; purée until smooth. Reserve half of mojo sauce (1/2 cup); generously season fish with salt and evenly coat in remaining mojo sauce.
Preheat grill for direct-heat cooking. Arrange citrus rounds in a single layer on grill grates in an oblong pattern slightly larger than fish. Place salmon atop citrus rounds, skin-side down. Cover grill; cook until fish turns opaque and is just cooked through, 10 to 15 minutes, depending on thickness. Transfer fish and grilled citrus rounds to a platter. Serve with reserved mojo sauce.
The sauce can be made up to a day in advance and refrigerated in an airtight container.