Spinach and Avocado Toast

One of my favorite breakfasts:

Called tartine if you want to be fancy – a tartine is a slice of bread with a sweet or savory topping.

1 medium bunch spinach, coarsely chopped
¼ onion, chopped finely
1 T. olive oil
Salt and pepper to taste
2 slices whole grain bread
Grainy brown mustard
2 oz. your choice of cheese
½ avocado (optional)
Sriracha (optional)

Saute onion and spinach in olive oil until the spinach wilts. Salt and pepper to taste. Toast bread, spread with mustard and pile on spinach and avocado if using. Top with cheese. Broil until cheese melts.