Heat olive oil in a saucepan over medium heat.
Add chopped onions and sauté until translucent.
Stir in the chopped tomatoes and cook for about 5 minutes.
Add apple cider vinegar and brown sugar, mixing well.
Season with salt, garlic powder, allspice, cinnamon, and black pepper.
Bring the mixture to a boil, then reduce heat to low.
Simmer uncovered for about 20-25 minutes, stirring occasionally.
Once thickened, remove from heat and let it cool slightly.
Transfer to a blender and blend until smooth.
Pour the ketchup into a clean jar and refrigerate.