How to Make It
In a large bowl, whisk the milk with 1/2 cup of the flour and the adobo sauce until smooth. Add the onion rings and toss to moisten with the mixture.
In a cast-iron skillet, heat the oil to 350°. In a large paper bag, combine the remaining 1 cup of flour with the cornmeal, cumin and 1/2 tablespoon salt. Working in batches, dredge the onions in the cornmeal mixture, shaking off the excess. Transfer to a baking sheet.
Working in batches, fry the onion rings in the hot oil until golden brown, 3 to 4 minutes. Using tongs, transfer to paper towels to drain. Season with salt and serve immediately.