In a medium bowl, whisk together eggs, milk, cumin, salt and pepper.
In a skillet, melt butter. Add potatoes and onions and cook about 8 minutes until potatoes are almost tender.
Add spinach, season all vegetables and cook about 1 minute until spinach is just wilted.
Pour egg mixture into the skillet, and allow to start to set, then fold into the vegetables. Cook until eggs are done to your likeness.
Serve with hot sauce, if desired.