If you are using bamboo skewers for making the tikka kebabs, then soak the skewers in water for about 40 minutes. This will prevent the skewers from burning.
While the skewers are soaking, prep the baking tray by lining it with aluminum foil.
Now, after the soaking time, take the skewers out of the water and pat them dry.
Next, preheat the oven for around 15 -20 minutes at 240 ̊C.
In the meantime, thread the chicken pieces, bell peppers, and diced onions in sequence. Repeat this sequence for about 80% of the skewer.
Do this with all the skewers and when the oven is heated, place them on the tray. Make sure to have spacing between the skewers.
Grill them for about 10 minutes from one side and then turn to the other side using a tong. In between, brush them with melted butter. This will prevent the chicken from drying.
Do this until they are perfectly cooked from both sides. (Every oven has differences, so the timings may vary).
When it looks like done, take them out and check one piece of chicken by breaking it from the middle.
If it is cooked through, then transfer them onto a plate and go for the second batch.