In a large bowl, toss together the cabbage, cucumber, vinegar, olive oil, dill, salt, and pepper. Cover and refrigerate for at least an hour, allowing the flavors to meld.
Preheat oven to 425. Lightly oil a baking dish and place salmon skin-side down in the dish. Brush salmon with lime juice. Season the salmon with the chipotle powder, lime zest, salt, and pepper, lightly pressing in the seasonings so that they adhere. Roast for 12-15 minutes, depending on the thickness of the fish. Salmon is done when the fish is just flaky.
Warm the tortillas over an open gas flame on the stove or on a grill. To serve, arrange a portion of the salmon in the middle of each tortilla and top with the slaw and sliced avocado. Give an extra squeeze of lime and a drizzle of sriracha, if desired.
Lighlty adapted from Barefoot Contessa's Cooking for Jeffrey