Bring a large pot of salted water to a boil. Cook the pasta according to package directions, drain and set to one side.
1 pound rigatoni pasta
Place the oil in a large skillet and place on a medium high heat. Once hot, add in the diced onion and garlic, along with a pinch of salt and black pepper. Cook til softened.
1 teaspoon oil, 1 large onion, 2 large garlic cloves
Push the onions and garlic to one side of the skillet, and place in the ground beef, along with ½ teaspoon salt and ¼ teaspoon of black pepper.
1 pound ground beef (medium or lean)
Cook the ground beef, whilst breaking up with a spatula, til no pink is left.
To the beef, add the tomato paste, pesto, lemon zest and cream. Stir together well and bring the cream to a simmer.
1 tablespoon tomato paste, 1 jar green pesto, zest 1 lemon, 1 cup cream (35%)
Simmer for 15 to 20 minutes til the cream has thickened, stirring occasionally so that the bottom doesn't stick.
Place the cooked pasta into a large pot and add in the creamy beef. Stir together.
Serve with a garnish of grated parmesan and fresh herbs like parsley or basil.