Heat the skillet over medium-high heat. Add olive oil, red onion, and cherry tomatoes. Cook tomatoes until they begin to blister and split, tossing occasionally, about 10 mins.
Using tongs or the back of a spoon pop the tomatoes. Add garlic, sauté until fragrant and tomatoes have released their juices, about 3 minutes.
Add tomato paste, vinegar, salt, and harissa. Mix until well combined and saucy. If you like your food with a little more spice you can add more harissa to taste.
Add shrimp and parsley, sauté until shrimp is cooked through, about 5 minutes.
Serve with crusty bread, pasta, or polenta. Garnish with fresh parsley.
