Preheat your oven to 375 “F. Meanwhile bring a large pot of water to a boil and salt it well. Add the ravioli and cook them for 2 minutes until they float to the top, or according to the instructions on the package. Cook 1 minute less then whatever the box says.
Drain the ravioli in a colander and drizzle them with a lug of olive oil so they won’t stick to each other. Work with them gently as not to break them, set aside.
In a large skillet heat up a lug of olive oil and roast the garlic cloves on low flame until golden all over, making sure not to burn them. Once the garlic is golden add in the baby spinach and toss to coat in the oils for about a minute until wilted. Season with a pinch of sea salt. Transfer to a colander and allow the moisture to drain well.
meanwhile, In a small bowl whisk together the ricotta cheese with a pinch of salt and 1 tbsp of the olive oil until smooth.
Take out your large gratin pan, and pour in a drop of olive oil and 1/2 c of the tomato sauce. Spread it all over the bottom. Top with half of the ravioli slightly overlapping them. Drizzle another 1/2 c of tomato sauce of the ravioli and top with the ricotta cheese. Sprinkle the sautéed spinach and roasted garlic all over the top of the ricotta cheese, the sprinkle a half of the fontina cheese on top. Layer the remaining ravioli over the top, slightly overlapping each other, and top with he remaining half cup of the tomato sauce. Sprinkle the remaining fontina cheese all over the top and bake in the preheated oven for 10 minutes, until the cheese has melted.
For a golden top, transfer the lasagne to a preheated broiler for a couple of minutes, until golden brown to your liking. Allow the lasagne to cool off and set for about 10 minutes before serving garnished with fresh basil or parsley.