Toast macadamias.

Chop garlic.

Combine macadamias and garlic in a food processor.

Process until finely chopped.

Add arugula, olive oil, lemon juice, and vegetable stock to the food processor.

Process until almost smooth to make the pesto.

Cook penne pasta in boiling salted water according to package directions.

Drain pasta, reserving 2 tbsp of cooking water.

Return penne pasta and reserved pasta water to the saucepan.

Add tuna, pesto, and lemon peel to the pan.

Cook on low heat, tossing gently, until well combined and heated through.

Serve with lemon wedges.