I believe the cuvette would be the tri-tip in America. On the Danish butcher chart, the cuvette is definitely shown coming from the region that would correspond to "bottom sirloin" on an American chart.
If you search for cuvettestege and look at the images, it is pretty clear.
http://fjordrejen.dk/wp-content/uploads/udskæring.jpg
Tri-Tip is similar shape, similar grain pattern:
http://2.bp.blogspot.com/-9jR8uufNdEw/UFNldiLjXKI/AAAAAAAAA0E/HJtRy0lN_PU/s1600/tri_slicing.jpg
The only other possibility was that I saw a photo of a cut called "sirloin tip eye". One or two photos looked exactly like cuvette in the Danish butcher chart, but I suspect that sirloin tip eye is the same muscle(s) as tri-tip.