Can I hold a strainer and have my husband pour macaroni from a pot through it during nidda?

If you don’t have another easy alternative, then it is permissible.

Although touching and passing are prohibited during nidda, indirect touching or passing are permitted in a time of need. For example, placing something in a handbag she is holding would be permitted in a time of need, since he is not directly passing to her rather putting it in her bag.

In this case, there is even more room to be lenient since he is only pouring the macaroni, which might be considered more like throwing than passing. Also, it is very indirect, since he is pouring something from a pot into a strainer she is holding, and neither are giving or receiving directly in their hand.

See Taz (Y.D. 195:8) who permits in a similar case.