Gather your supplies
Spray pan with Pam and place mushrooms in.
Sautée spinach in pan in own juice stirring often over medium heat for approximately 10 min til it turns dark green and dries out.
Remove from heat , add the basil and 1/2 the mozzarella cheese.
Spoon mixture onto the mushrooms.
Add sliced tomatoes and broil on low about 10 minutes, checking often. When the tomatoes soften a little add the mozzarella. Cook another 5 minutes.