Roast the pine nuts in a pan without fat until golden brown, take them out. Clean the celery, peel the carrots, wash both and dice them finely. Prepare pasta in boiling salted water according to package instructions.
Wash lemon hot, grate dry, tear off zest. Halve the lemon and squeeze one half. Melt butter in a large pan. Fry the vegetable cubes for 3-4 minutes at low heat.
Meanwhile, wash the sage, dab dry and, except for something to garnish, pluck leaves from the stalks and add the pine nuts, lemon juice and zest to the vegetables and toss. Drain the pasta and fold into the vegetables, season with salt, pepper and possibly a pinch of sugar.
Arrange and garnish with remaining sage.