Heat oil in a medium saucepan over medium heat. Add onions, garlic and red pepper flakes and cook—stirring occasionally for 5 minutes or until onion starts to soften.
Add potatoes and cook, stirring occasionally for an additional minute. Add broth and bring to a boil.
Reduce heat and simmer covered for 10-12 minutes, until potatoes are cooked through and soft. Add spinach, peas and cilantro, and cook uncovered for an additional 5 minutes, until peas are heated through.
Puree soup with a blender and season with salt and pepper.