Finely dice the onion and crush the garlic. Heat the olive oil in a skillet over a medium/high heat. Add the ground pork, onion, and garlic. Cook until the pork has browned all over.
Add the oregano and tomato paste to the skillet. Season everything with salt and pepper. Stir well to combine and cook for a minute more. Remove the mixture from the skillet and transfer it to a bowl.
Add the chopped tomatoes and stock to the skillet. Season with a little salt and pepper as desired. Stir well to combine. Bring to a gentle boil, then simmer for 5 minutes.
While the sauce is simmering, slice the zucchini from the base creating 8, 1 inch thick discs. Take a knife and carefully score a cross in the zucchini and score gently around the edge, leaving a 1/4 inch border. Carefully hollow out the zucchini with a teaspoon leaving a 5mm thick base.
Preheat the oven to 375 degrees. Divide the pork mixture evenly between the hollowed zucchini discs. Pack each one tightly with the mixture.
Nestle the stuffed zucchini rings into the skillet in amongst the tomato sauce. Transfer the skillet to the oven. Bake for 25-30 minutes. The sauce should be reduced right down and the zucchini tender.
Roughly chop the fresh basil. Scatter the basil over the stuffed zucchini. Serve hot with your preferred Keto sides.