Cook carrot in water to cover in a large saucepan over medium-high heat 20 to 25 minutes or until very tender; drain well.
Process carrot and eggs in a blender or food processor until smooth, stopping to scrape down sides.
Add 2/3 cup sugar, matzo meal, 1/2 cup butter, salt, nutmeg, and vanilla; process until smooth. Pour mixture into a lightly greased 13- x 9-inch baking dish.
Bake at 350° for 40 to 45 minutes or until set. Combine remaining 1/3 cup sugar, 1/4 cup butter, and walnuts. Top soufflé with mixture; bake 5 to 10 more minutes.
* 1 (2-pound) package sliced frozen carrots may be substituted for fresh carrots.