Ground almond/cashew replacement

That is unusual for a chicken tikka recipe which usually uses dairy for that creamy texture.
Raw sunflower seeds work great as a sub for cashews, note that if you’re blending them it’s important they’re raw and soaked for a few hours to make a creamy texture.

Toasted pumpkin seeds should work well.

Not the recipes I know.
Maybe some are adding the ground nuts as a thickener for the sauce.
Have a look at this nice review article and combination recipe from The Guardian (UK recipe columnist Felicity Cloake) and see if you like the way it sounds.
https://www.theguardian.com/lifeandstyle/wordofmouth/2014/apr/24/how-to-cook-perfect-chicken-tikka-masala
If you still want the crunch or thickening that the almonds or cashews would give, add a nut or seed you can tolerate, or some bread or crackers (croutons, crumbs or whatever you like).