Pre-heat a grill over medium-high heat. Brush the corn with olive oil and season with salt and freshly ground black pepper. Grill the corn until the kernels start to char, about 7 to 10 minutes on an outdoor grill (longer on an electric grill). Remove the ears of corn from grill and let them cool for a few minutes before removing the corn kernels from the cobs using a knife or a mandolin. Place the grilled corn kernels in a bowl.

Lightly oil the scallions and pop them on the grill for about 3 minutes per side and remove from the grill. Chop the scallions, leaving the green ends a bit longer than the white ends. Add the chopped scallions, Jalapeño pepper, lime juice, and cumin to the bowl with the corn and toss to combine. Stir in the fresh cilantro and season with salt.

Rub the tuna steaks with a little olive oil and season with chili powder and salt. Grill over high heat for 2 minutes per side until the tuna is rare, or a minute or two longer if you want the tuna cooked more well-done.

Slice the tuna steaks into thick slices or leave them whole and top with some sweet corn salsa. Serve the remaining salsa with chips.