Process beans in food processor until smooth. Combine pureed beans, ground beef, oregano, cumin, and garlic powder.
Arrange 8 lasagna noodles in bottom of steamtable pan. Spread ¼ of the bean mixture over noodles; sprinkle with 2 cups cheese.
Repeat layers, using 8 lasagna noodles and ¼ of the bean mixture and 2 cups cheese; top with remaining 8 lasagna noodles. Repeat with second steamtable pan, using remaining noodles, bean mixture, and cheese.
Mix salsa and water; pour half over each pan of lasagna. Bake, covered with aluminum foil, at 350º F until lasagna is hot through and pasta is tender, about 1½ hours. Uncover and sprinkle each pan with remaining 2 cups cheese; bake until melted, 5 to 10 minutes longer. Cut into squares to serve.