Cut off the pointed part of the onion and peel it. Place the onion on a work surface, cut-side down and make downward cuts into the onion, starting 1/2 inch from the root, all the way to the work surface. Repeat 7 more times, making a total of 8 evenly spaced cuts around the onion.
Turn the onion over and gently separate the outer pieces, using your fingers.
Whisk milk, water, eggs, and a pinch of salt together in a bowl.
Whisk flour, cayenne pepper, and a pinch of salt in a separate bowl.
Preheat oven to 200 C.
Heat the vegetable oil in a deep pan to 200 C.
Dip the onion in the egg mixture, then remove and place the onion into the flour mix, using your hands to make sure you cover all of the onion and it’s ‘petals’.
Lift the onion out of bowl by the core, patting to release excess flour. Fully submerge the onion in egg mixture again; remove and place back into the bowl of flour. Coating the onion again with flour mixture.
Turn the onion cut-side down and place in a slotted spoon.
Carefully lower onion in the hot oil and fry for 5 minutes; carefully turning the onion over and cooking until golden brown. Remove and drain on paper towels and season with salt.
Place the onion in a cast iron pan and top with 1/2 of the cheddar cheese followed by the bacon, and then the remaining 1/2 of the Cheddar cheese.
Bake in the preheated oven until cheese is melted, 3 to 4 minutes. Drizzle ranch dressing over onion and sprinkle with spring onions, chives and pepper.