In a bowl, make a salsa by combining cucumbers, tomatoes, cilantro, olive oil, 1 tablespoon lime juice, lime zest, 1/2 teaspoon salt and a pinch of black pepper. Set aside.
Remove any remaining pin bones from the salmon, and season each fillet with a pinch of salt and pepper. In a bowl, whisk together agave, Worcestershire sauce, 1 teaspoon lime juice, and chipotle powder. Pour the mixture over the salmon, the cover and chill at least 20 minutes.
Preheat broiler to high and adjust rack 6 inches from the heating element.
Slice squash on the bias into 1/2 inch slices. Toss with garlic, vegetable oil, 1/2 teaspoon salt and a pinch of black pepper. Remove the salmon from the marinade.
Heat an enameled cast iron skillet over medium-high heat. Once hot, add the squash in one even layer and sear for 2 minutes. Carefully flip the squash, then top with the salmon, skin side down.
Place in the oven and broil 5-6 minutes, the check for doneness. A thermometer inserted into the thickest part of the fillet should read 130°F.
Serve salmon and squash garnished with the cucumber-tomato salsa.