Combine water and oats in a small saucepan. Bring to a boil, then reduce heat to medium and simmer for 3 to 5 minutes, stirring occasionally, until desired texture is achieved.
Stir in the nutritional yeast, oil, salt, and pepper. Remove from heat and scoop into a large bowl or divide into two small bowls. Top with tomatoes, avocado and a handful of baby spinach. Serve immediately.