Hi Ulla,
Here is a recipe I found in Taste of Home,
I haven't tried it yet but it sure sounds
good.

Lasagna with White Sauce

1 pound ground beef
1 large onion, chopped
1 can(14-1/2 oz)tomatoes with liquid,cut up
2 Tbs. tomato paste
1 beef bouillon cube
1-1/2 tsp. Italian seasoning
1 tsp. salt
1/2 tsp. pepper
1/4 tsp. ground red or cayenne pepper
White Sauce:
2 Tbs. butter or margarine
3 Tbs. flour
1 tsp. salt
1/4 tsp. pepper
2 cups milk
1-1/4 c shredded mozzarella cheese, divided
10 to 12 uncooked lasagna noodles

In a Dutch oven, cook beef and onion until
meat is browned and onion tender; drain.
Add tomatoes, tomato paste, boullion, and
seasonings. Cover and cook over medium-low
heat for 20 minutes, stirring occasionally.
Meanwhile, melt butter in a med. saucepan;
stir in flour, salt and pepper. Add milk
gradually; bring to a boil, stirring
constantly. Reduce heat and cook for 1 min.
Remove from the heat and stir in half of the
cheese; set aside. Pour half of the meat sauce
into an ungreased 13x9 baking dish. Cover
with half of the lasagna noodles. Cover with
remaining meat sauce. Top with remaining
noodles. Pour white sauce over noodles.
Sprinkle with remaining cheese. Cover and
bake at 400 degrees for 40 min. or until
noodles are done.