-
1
Preheat oven to 350F.
-
2
Butter a 15- by 10- by 1-inch shallow baking pan and line with wax paper.
-
3
Butter paper and dust with flour, knocking out excess.
-
4
Beat together yolks, vanilla, and 5 tablespoons granulated sugar in a large bowl with an electric mixer at high speed until thick and pale, about 1 minute with a standing mixer or 3 minutes with a handheld.
-
5
Beat whites with salt using cleaned beaters in another bowl until they just hold soft peaks.
-
6
Add remaining 3 tablespoons granulated sugar, a little at a time, beating until whites just hold stiff peaks.
-
7
Gently fold one third of flour and one third of whites into yolk mixture, then gently fold in remaining flour and whites in 2 more batches, making sure flour is thoroughly incorporated.
-
8
Spread batter evenly in baking pan and bake in middle of oven until top is pale and dry to the touch, 10 to 12 minutes.
-
9
Transfer cake in pan to a rack and cool, covered with a kitchen towel, 5 minutes.
-
10
Cook rhubarb with sugar in a 12-inch nonstick skillet over moderately high heat (rhubarb will exude liquid), stirring, until rhubarb is a thick puree, about 8 minutes.
-
11
Spread filling on a plate and chill 5 minutes.
-
12
Remove towel and arrange cake with a short side nearest you.
-
13
Spread rhubarb filling evenly over cake, leaving a 1-inch border on each short side.
-
14
Put a platter next to far end of cake.
-
15
Beginning with near short side and using wax paper as an aid, roll up cake jelly-roll style.
-
16
Carefully transfer roll, seam side down, to platter, using wax paper as an aid.
-
17
Dust cake generously with confectioners sugar, then slice with a serrated knife.
