Preheat oven to 350 degrees.  Using a dutch oven heat saute sliced onions in 2 tablespoons of vegetable oil.  Add about 1/2 teaspoon salt to the onions.  Saute onions until they are translucent.  Remove onions from pan.  Sprinkle both sides of the brisket with salt and pepper.  Place brisket into pan brown on both sides.  Once brisket is browned on both sides, remove brisket from pan.  Pour in 1 cup of beef broth into pan, scrape brown bits from the bottom of the pan.   Add two tablespoons of tomato paste, and whisk together well.  Place onions, and then the brisket back into the pan, add enough broth to the pan to cover the brisket half way.  Bake brisket for approximately 3 1/2 hours.  The brisket is done when a fork slides into the meat easily.  If the meat is still tough after the initial baking bake for an additional 30 minutes.  Once the brisket is removed from the oven, let rest for approximately 20 minutes before slicing.

Prepare lasagna noodles as directed on the package.  To use the noodles for the baked pasta dish, once the noodles are done, they need to be cut in half vertically, and horizontally.  This way you don't have to eat a whole lasagna noodle in one bite.

For the sauce combine heavy cream and butter in a sauce pan over medium to medium high heat.  Once the butter and cream just begin to simmer, whisk in all cheeses.  The sauce will thicken, remove pan from heat.  Place noodles into a 2 quart casserole dish.  Arrange the noodles by folding them over so they make nice curls.  Pour sauce over the noodles.   Toss spinach with olive olive, and then place the spinach around the sides of the casserole dish.  Place 6 to 8 ounces of beef over the noodles.  You may want to spoon a little of the cooking gravy from the brisket over the beef.  Top with a little Asiago and Fontina cheese and place back into the oven for 10 to 15 minutes until the cheese melts on the top of the pasta.

I do not recommend making the pasta and sauce portion ahead of time.  You can make the brisket ahead of time.