Grease 8x4-inch loaf pan.
Line bottom with parchment or waxed paper; grease paper. Cook carrots until softened, drain. Let cool.
In nonstick skillet, melt butter over medium heat; cook garlic and onion, stirring until very soft.
Let cool completely. In food processor or blender, purée onion mixture, carrots, lemon rind. Lemon juice, nutmeg, salt and pepper until smooth; transfer to large bowl.
Whisk together eggs and evaporated milk. Add to carrot mixture, blending well.
Pour into prepared pan, smoothing top. Cut rectangle of parchment to fit directly on top of mixture.
Place loaf pan in large pan. Pour in boiling water to come halfway up side of loaf pan.
Bake in 350 degree oven for about 1 1/4 hours or until center of terrine is firm to the touch and knife inserted in center comes out clean.
Remove loaf pan from water; peel off top paper. Run knife around sides of pan. Let stand 10 minutes.