Combine tomatoes, garlic, basil (including stems), walnuts, and red pepper flakes into blender for food processor and pulse until combine. Gently add in oil and pulse until well mixed.
In sauce pot bring water to boiling and add polenta, stirring with whisk for 2-3 minutes. Allow to cook on medium low heat stirring every few minutes until done, about 20-30 minutes.
Whisk in tomato pesto into hot polenta and stir to combine and serve.