Preheat oven to 375 degrees F. For filling, in an extra-large skillet, cook fennel and garlic in hot oil over medium heat for 3 to 4 minutes or until tender. Add spinach; cook, covered, about 2 minutes or until wilted. Transfer spinach mixture to a sieve; press out excess liquid with the back of a spoon. In a large bowl, combine egg, ricotta cheese, Parmesan cheese, Italian seasoning, and lemon peel. Stir in spinach mixture.
Spread half of the marinara sauce over the bottom of an ungreased 3-quart rectangular baking dish. Spoon about 1/3 cup of the filling along the center of each crepe; roll up crepe. Arrange crepes, seam sides down, on top of marinara sauce in dish. Spoon the remaining marinara sauce over crepes down center of dish. Pour Alfredo sauce over crepes, spreading evenly. Sprinkle with fontina cheese.
Bake, uncovered, for 25 to 30 minutes or until bubbly around the edges. Let stand for 10 minutes before serving. Makes 5 servings.