Marinade chicken in lemon and salt: Chop the chicken tenders into bite-sized ("tikka") pieces. Place chicken in a single layer in a shallow food storage container. Add the lemon juice and salt. Stir to mix, or, cover securely and shake to mix. Store covered in the refrigerator for 1 hour.
Marinade chicken in yogurt: in a small bowl, mix together the yogurt, garlic, ginger, garam masala, salt, white pepper, chili powder, cumin, and oil. Pour this onto the chicken. Stir to mix, then cover the chicken and refrigerate for 4 hours.
Bake chicken: Preheat the oven to 350 degrees Fahrenheit. Transfer the chicken to an oven-safe pan or cast iron skillet; spread into a single layer. Bake the chicken, uncovered, for ten minutes; remove from oven, drizzle with 1 tbsp vegetable oil, then return to oven and bake for another 10 minutes.
Saute onion: while the chicken is baking, heat 1 tbsp vegetable oil in a 6 quart stock pot on high heat. Add the chopped onion; saute the onion until the onion is translucent and has slightly browned edges. Add about 1/4 cup of water, then add the ginger, garlic, cumin, coriander, turmeric, chili powder, garam masala, and salt. Stir to mix.
Add chicken and make sauce: Remove chicken from oven; use tongs or a slotted spoon to take chicken out of baking pan and place into stock pot. Saute chicken for 3 minutes on low to medium heat. Add in the green chilies, tomato puree, and lemon juice; stir to combine, and bring to a boil. Add butter; remove stock pot from heat, and stir until butter is melted.
Cool and add cream: Let the stock pot sit at room temperature for 10 minutes, and then mix in the cream.
Serve with steamed white rice, and garnish with chopped green coriander.