Easy and delicious (good for when you totally forgot the leafy green side dish till the last moment):
A couple handfuls amaranth greens, per person
1/4-1/2 tsp black and/or yellow mustard seeds, per person
1 tbsp sliced almonds, per person
Toast almonds in a wide pan over medium-high heat, stirring or tossing frequently. Just as they begin to brown, add a tablespoon or two of olive oil and stir to coat, then immediately add the mustard seeds. Stir and fry for a few seconds, then add the amaranth greens. Cook for 2-3 minutes, stirring occasionally and pressing the leaves against the pan for a few seconds from time to time. Add a tablespoon or so of water, cover the pan, and let steam for few moments till the water evaporates, then uncover, sprinkle with a little salt, and serve.