Here is the link to Flaming Durtles but I realized it’s only on Android so if you have an iPhone, you can check Jakeipuu and Tsurukame. I don’t know if these ones have an Anki mode though.
In Anki mode, you don’t have to write the answer, you just answer it aloud or in your head, click on Show answer, then on Correct or Incorrect. There is also a userscript to have Anki mode directly on the website but I have not tested it yet.