Heat olive oil in a large pot or Dutch oven over medium-high heat.

Brown pork spareribs in the hot oil on all sides.

Remove the spareribs from the pot and set aside.

Add chopped onion to the pot and sauté until softened and translucent.

Add minced garlic to the pot and sauté until fragrant.

Pour in canned plum tomatoes and water.

Stir in tomato paste, salt, pepper, dry oregano, garlic powder, and fennel seeds.

Return the browned spareribs to the pot.

Bring the sauce to a boil, then reduce heat to low.

Simmer uncovered for 2 hours, or until the meat is very tender and falling off the bones, stirring occasionally to prevent burning.

Remove spareribs before serving.