Bring a large pot of salted water to a boil and cook the spaghetti according to package directions until al dente.
While the pasta cooks, drain the canned tuna and dice the lean ham into small cubes.
Heat the olive oil in a large skillet over medium heat, then add the minced garlic and diced ham, sautéing for 2-3 minutes until fragrant.
Stir in the green peas and tuna, heating through for another 2 minutes.
In a small mixing bowl, whisk together the Greek yogurt, lemon juice, sea salt, and black pepper until the sauce is smooth.
Reserve 2 tablespoons of the starchy pasta water, then drain the spaghetti.
Remove the skillet from the heat to prevent the yogurt from curdling, then add the cooked pasta and the yogurt mixture.
Toss everything together quickly, adding the reserved pasta water as needed to create a silky coating.
Garnish with freshly chopped parsley and serve immediately.