Steps
1. Slice the onion into thin rings.
2. In a skillet, heat olive oil over medium heat.
3. Add the sliced onions, sprinkle with salt, and cook until they are soft and caramelized, about 10-15 minutes.
4. Stir in the paprika and cook for another minute, then remove from heat.
5. Toast the slice of bread until golden brown.
6. If using, place the cheese on the toasted bread and top with the caramelized onions.
7. Garnish with fresh parsley if desired, and serve warm.