In a deep fryer or a large, heavy pot, pour in enough vegetable oil to submerge the onion balls, heating it to 350°F (175°C). Prepare a plate lined with paper towels to drain the fried onion balls later.

Finely dice the yellow onions, aiming for small, uniform pieces. Pat the chopped onions dry with paper towels to absorb any excess moisture.

In a medium bowl, combine the chopped onions with all-purpose flour, baking powder, salt, black pepper, garlic powder, and paprika. Gradually add milk, mixing until a thick batter forms. Let rest for 2-3 minutes.

Carefully drop spoonfuls of the batter-coated onions into the hot oil and fry for 3-4 minutes or until golden brown. Use a slotted spoon to remove them and let drain on paper towels.

While the onion balls cool slightly, mix ranch dressing and Cajun seasoning in a small bowl to create the dipping sauce.