First Night in Florence Spaghetti

Name: First Night in Florence Spaghetti
Ingredients: 1/2 package spaghetti or bucatini; Sea or kosher salt; Good olive oil, and lots of it; 1 pint cherry or grape tomatoes of whatever colors are to hand, halved; A couple of generous handfuls of fresh spinach, stems pinched off; Juice of 1/2 lemon, Meyer if possible; Sea or kosher salt and pepper to taste; A good Pecorino Romano cheese; 1 can tuna packed in olive oil, typically 5 to 6 ounces - not drained!; 2 cloves garlic smashed, peeled, minced