In a large skillet, heat the vegetable oil over medium heat. Add the diced onion and sauté until translucent, about 5 minutes.
Stir in the minced garlic and cook for an additional minute until fragrant.
Add the sliced okra to the skillet and cook for about 5 minutes, stirring occasionally, until it begins to soften.
Mix in the diced tomatoes, salt, black pepper, paprika, cayenne pepper (if using), apple cider vinegar, and water.
Bring the mixture to a simmer, then reduce the heat to low. Cover the skillet and let it cook for 15-20 minutes, stirring occasionally, until the okra is tender.
Taste and adjust seasoning if necessary. Remove from heat and garnish with chopped parsley before serving.