Preheat oven to 350° F.
In a large mixing bowl, whisk eggs and heavy cream for 2 minutes until light and fluffy. Add onions, parsley, dill, salt and pepper. Fold in spinach and Colby cheese.
Heat a 10-inch, cast-iron skillet; melt butter in skillet. Lower heat to medium-low, pour in egg mixture. With a wooden spoon, stir bottom of skillet, loosening cooked egg. Take skillet off heat and place in oven; bake for 45 minutes or until the quiche does not move when the skillet is shaken.
Serve warm atop field greens, such as arugula or mesculin greens. Or, top with toasted pine nuts and drizzle with olive oil.Servings: 8