Peel the onions and slice them into 1/4-inch thick rings, separating each layer.
In a shallow bowl, mix together the flour, salt, pepper, and paprika.
Pour the buttermilk into another shallow bowl.
Heat the vegetable oil in a large skillet over medium-high heat until it reaches 350°F.
Dip each onion ring into the buttermilk, allowing the excess to drip off, then coat it in the flour mixture.
Fry the onion rings in batches, turning occasionally, until golden brown and crispy, about 3-4 minutes per batch.
Remove the fried onion rings and drain on paper towels.
While the onion rings are still hot, sprinkle the shredded cheddar cheese over them, allowing the cheese to melt slightly.
Serve immediately and enjoy the crispy, cheesy goodness.