1. Bring 1 1/2 cups cold water and amaranth to a boil in a medium saucepan; reduce heat, cover, and simmer 20 minutes or until water is almost absorbed (it will have the appearance of mush).
2. While amaranth cooks, combine cucumber and next 11 ingredients in a large bowl.
3. Place amaranth in a sieve, and rinse under cold running water until room temperature; drain well, pressing with the back of a spoon. Add to cucumber mixture; toss to blend. Add cheese; toss gently. Garnish with lemon wedges, if desired.