Preheat the oven to 200C. Prepare a muffin tin pan. Grease it with generous amount of cooking oil spray. Keep it aside.
Wash and peel the potatoes. Grate the potatoes using a grater with big holes. Mix it with salt and lemon juice. Leave it in a colander to drain for at least 20 minutes.
After 20 minutes, squeeze out the excess water by pressing the grated potatoes and pat it dry.
Heat a pan and add butter or oil. When the oil starts to simmer, add onions, ginger and garlic and saute till the onions turn soft and translucent. Add the spinach, cayenne, tandoori masala powder and salt as per taste.
Saute till there is no moisture in the spinach . Turn off the heat and keep it aside.
Arrange the grated potatoes in the greased muffin tin pan and press it against the bottom and up the sides of each muffin tin in the form of a nest. Spray cooking oil on the inside of the potatoes nest in each muffin cup.
Bake in the preheated oven for 15 minutes or till the edges turn golden and light brown in colour. Take it out from the oven and allow it to cool in the pan.
In a separate bowl,beat the eggs. Add a pinch of salt and the sauteed spinach. Stir and mix. Pour the spinach mixture filling into the potatoes nests. Bake for 10 minutes or until the egg is cooked.
Allow the potatoes spinach nests to cool for few minutes. Run a butter knife along the edges of the nest and carefully unmold the potatoes spinach nest. Serve it immediately.