Fill a large pot with oil halfway up the pot. Heat oil to 350 degrees F. Preheat grill.
In a medium bowl, mix together 1 cup flour, cumin, cayenne, and salt. Slowly whisk in beer until thick, but not runny. Dredge fish in remaining flour first, then dunk in the batter. Fry in batches until golden brown, about 5 minutes. Drain on paper-toweled lined plate.
Meanwhile, grill tortillas on grill.
Serve fish in tortillas topped with Quick-Pickled Onion and Cucumber.
Quick-Pickled Onion and Cucumber:
In a medium saucepan, bring to a boil the vinegar, sugar, water, and salt. Add onions and cucumber and continue to cook a few minutes more. Remove from heat, add chile, and transfer to a bowl. Let cool slightly then chill covered, for at least 1 hour.
Toss in the tomato and cilantro, 5 minutes before serving.