Cheese Shrimp Penne Pasta & Spinach

8 oz (1/2 pound) penne pasta

7 oz (about 1/2 pound) large shrimp, peeled and deveined

2 cups fresh spinach, washed and roughly chopped

2 cloves garlic, minced

1 cup heavy cream or half-and-half

1 cup grated Parmesan cheese

1/2 cup cherry tomatoes, halved (optional)

2 tbsp olive oil or butter

Salt and pepper, to taste

Red pepper flakes (optional, for a bit of heat)

Fresh basil or parsley, for garnish