For the sauce: Heat the canola oil in a medium sauté pan over high heat. Add the Spanish onion, Granny Smith apple, and Mesa Curry Powder and cook until the onions and apples soften, stirring occasionally, about 5 minutes. Add the fish stock, bring to a boil, reduce the heat, and simmer, uncovered, for 20 minutes.
Add the coconut milk and three-quarters of the corn kernels. Simmer, uncovered, until slightly thickened, another 25 to 30 minutes. Strain the finished sauce into a large bowl, add the remaining corn, and taste for seasoning.
Preheat a grill for direct and indirect grilling. Brush the halibut on both sides with canola oil and sprinkle with salt and pepper. Grill over medium-high heat until slightly charred on the first side, about 4 minutes. Flip and char the other side, another 4 minutes.
If the fish is not yet cooked through, rotate the grate (instead of moving the fish) so that the fish is over indirect heat. Cover and cook another few minutes until just cooked through.
Transfer the cooked fish to a large serving platter. Ladle over some of the corn-coconut curry sauce. Scatter the herbs over the sauce, and then top with some Grilled Cherry Tomato Chutney.
Prepare a charcoal grill for direct grilling, high heat. Toss the grape tomatoes with canola oil and season with salt and black pepper. Transfer to a grill basket and grill until charred and slightly soft, tossing occasionally, about 5 minutes.
Combine the cider vinegar, light brown sugar, coriander seeds, and cumin seeds in a small saucepan and bring to a boil. Reduce the heat and simmer until thickened to a glaze, about 10 minutes. Let cool slightly, then pour over the tomatoes. Toss, mashing the tomatoes slightly. Add the herbs and the zest, toss again, taste and season.
