Simple One-Pan Sausage Skillet

1 can canned fire roasted diced tomatoes

1 cup baby spinach

1 cup shredded italian blend cheese

1 pkg beef smoked sausage

1 box rotini pasta

2 cloves garlic

2 tsp corn starch

1/2 whole sweet onion

1 tbsp butter

4 cups chicken broth

1/2 cup heavy cream