Once your chicken has marinated, preheat an oven to 220°c/200°c fan (428°f/392°f).
In the meantime, get the curry sauce on. To do this, first place a large saucepan over a medium-low heat & add in the 2 tbsp of oil & allow to heat up for a minute or two.
Add the butter into the pan then once melted, add in the sliced onion with a good pinch of salt. Cook until soft & translucent, stirring regularly. This will take at least 10 minutes.
Next, add in the tomato paste, cook for 2 minutes then stir in the rest of the tikka masala paste. Continue cooking for another 2-3 minutes, until fragrant.Make sure to stir the onions frequently to stop them catching on the bottom of the pan! Stir in the passata & water then bring the sauce to a gentle simmer. Cook, stirring occasionally until you have a thick, well cooked out sauce. This will take 15-20 minutes.Use the water to rinse out any passata left in the container it came out of. Whilst the sauce is cooking, take the chicken out of the marinade, place onto a lined baking tray then bake in the preheated oven until just cooked through. This will take 15-20 minutes.Once cooked, let the chicken rest for 10 minutes or so, whilst you finish the sauce.A digital food probe comes in handy here! The chicken's internal temperature should be 75°c/167°f once cooked through. Add the honey & lemon juice into the curry sauce then season the sauce with salt, to taste. Add in half of the chopped coriander then blitz smooth with a blender.
Stir the single cream through the sauce then set the pan over a medium-low heat. Bring to a gentle simmer then cook for 2-3 minutes until thickened to your desired consistency.
Whilst the sauce is thickening up, cut the chicken into bitesize pieces, discarding any bones. Then once the sauce is ready, add in the chicken, along with any juices. Continue cooking for 3-4 minutes until warmed through.
Stir the remaining coriander through the sauce then serve immediately.