Toast coriander and cumin seeds in heavy medium skillet over medium-high heat until slightly darker in color and very fragrant, stirring often, 3 to 4 minutes. Transfer seeds to medium bowl; cool. Using spice mill or mortar with pestle, grind seeds to medium consistency (not powder). Pour seeds into 13x9x2-inch glass baking dish. Add 6 tablespoons olive oil, garlic, and 2 teaspoons lime peel. Whisk to blend. Add salmon to oil-spice mixture in dish. Turn to coat. Cover and chill at least 1 hour and up to 3 hours, turning salmon occasionally.
Position rack in top third of oven and preheat to 450°F Brush heavy rimmed baking sheet with oil to coat. Working with 1 fillet at a time, brush off enough excess spices to leave thin coating. Arrange fillets on prepared sheet, spacing 2 inches apart. Sprinkle with salt and pepper. Roast fillets until just opaque in center, about 7 minutes.
Meanwhile, whisk sour cream, lime juice, and remaining 3/4 teaspoon lime peel in medium bowl to blend. Season lime cream to taste with salt and pepper.
Arrange fillets on platter. Sprinkle each generously with chopped cilantro. Serve with lime cream.