Preheat oven to 350 degrees F.
Saute onions over medium heat, adding a little water to steam, if necessary.
Meanwhile, combine remaining ingredients, except artichoke hearts and spinach, in a blender and blend until smooth.
Add artichoke hearts and pulse until roughly chopped.
Stir in spinach and onions until incorporated.
Pour into an oven safe dish and bake for 30 minutes, or until bubbly.
Let sit 10 minutes before serving.
Serve with whole wheat or gluten free crackers, pretzels, crudites, sourdough bread, baked tortilla chips, or any other finger food you prefer.