1Preheat oven to 400˚ F.
2Heat oil in large skillet set over medium heat; cook spinach for about 3 minutes or until wilted. Let cool completely. Squeeze out excess moisture and chop finely.
3Combine mozzarella, Parmesan and Asiago cheeses; reserve ¼ cup and set aside. Using electric mixer, beat cream cheese until light and fluffy.
4Add yogurt, lemon zest, lemon juice, garlic, salt, pepper, cayenne (if desired) and remaining cheese mixture; beat until blended.
5Stir in spinach and artichokes. Scrape into greased 4-cup baking dish.
6Sprinkle with reserved cheese mixture.
7Place on baking sheet; bake for about 15 minutes or until heated through and top is golden brown and melted.
8Serve warm with crackers.
To make ahead, assemble dip, cover and refrigerate. Bake just before serving and serve warm.