Adey has already cleared up the quantities. It's 1 tsp of grated shatkora zest, and that is interesting to me, as this is where the flavour is concentrated (massively). The knowledge I have gained (from a chef) is that frozen peel/underlying pith should be hard-fried, to get the flavour out of it (for a BIR type dish). Frozen shatkora is rarely as good as fresh. When cooking a BIR dish using fresh peel/pith it can be added later, as it is inherently more pungent. I have made quite a few shatkora dishes, BIR and trad. The difficulty (for me) is that the stuff is so bloomin' zingy, it's hard to find the right taste/balance in the finished dish. Bitterness can be a "problem". Indeed, when chef Moike made a trad shatkora at my house, after I insisted on him doing so, it was still pretty tart. He knocked this up in about 2 hr. 1 kg mutton on the bone with 4 thin slices of very fresh shatkora. A mellow tasting shatkora bhuna really needs slow cooking (e.g overnight), apparently. Adey's recipe got me thinking that grated zest may be more conducive to BIR pan-type cooking, and I've not seen mention of this anywhere previously. I have also not seen a recipe on here that remotely resembles Adeys. Agree an original pic of the dish would be better, but it's no big deal. A lot of my curries look pretty similar, and so do most other peoples' efforts. I might start using stock photos myself ;D
Rob