Beat eggs, sour cream, milk and salt. Stir in onions.
Melt butter in 9x13 pan in the oven. Remove pan from oven. Tilt pan to spread butter. Pour ingredients into pan and return to oven. Bake 325° for 35 minutes or until center is set.
**ADDITIONS: cubed ham, sausage, Cheddar cheese. If you add any of these, omit the salt.