Red amaranth.
Because it contains amaranth, it will separate in case of heat. So red amaranth can dye the noodles red.
Amaranth, also known as wild goose red, young and old, tricolor amaranth, amaranth family, amaranth is an annual herb with thick, green or red stems, often branched, hairy or hairless when young. Amaranth has a soft and smooth body and a strong taste. It tastes sweet and has the effect of moistening the intestines and stomach and clearing away heat. It is also called "Mallard", "Crab", "Xingcai" and "Wucai". Some places are also known as "red mushroom tiger", cloud coriander, cloud day dish, corn dish, cold dish, Renqing, etc. Hubei, Anhui Guangde and other places are called Han cuisine.
Amaranth likes warmth and is relatively heat-resistant. The suitable temperature for growth is 23 to 27 degrees. It grows slowly below 20 degrees, and it is difficult for seeds below 10 degrees to germinate. The soil is required to be wet, but not resistant to waterlogging, and the air humidity is not strictly required. It is a short day vegetable, and is easy to bolt and blossom under the condition of high temperature and short sunshine. It is cultivated in spring when the temperature is suitable and the sunshine is longer, bolting is late, the quality is tender, and the yield is high.
Amaranth is native to China, India, Southeast Asia and other places. China has been used as wild vegetable since ancient times. Because of its strong resistance, easy growth, drought resistance, humidity resistance, high temperature resistance, and the rare occurrence of diseases and pests, amaranth is gradually recognized and developed by people both in China and abroad.