Curried Cauliflower and Potatoes

I am in love with my husband's cauliflower curry. He always makes it perfectly. I'm copying his recipe here so that hopefully I can make it on my own in the future. 

Ingredients: 

1 onion, chopped small 

1 large head of cauliflower, chopped into approximately 1/2-inch pieces

4 cloves of garlic, peeled and chopped coarsely

2 medium potatoes, diced small

3 Roma tomatoes, diced

1 cup of frozen peas 

1/4 cup coconut oil 

1 Tablespoon lemon juice

2 teaspoons curry powder 

2 teaspoons garam masala

1/2 teaspoon asafetida

1/2 teaspoon mango powder (optional)

2 teaspoons black cumin seed

1/2 teaspoon mustard seeds

1 teaspoon tumeric

1 1/2 teaspoon salt 

Directions:

1. Add one-third of the coconut oil to a large sauce-type pan. Raise heat to medium-high. Add cumin seed and mustard seed for 1 minute, until the seeds start to pop some but do not burn. Then, add onion. Saute until the onion begins to caramelized, approximately 5 minutes. Remove mixture from pan and set aside. 

2. Place one-third more of the coconut oil into the pan. Add the cauliflower, tumeric, 1 teaspoon salt, and saute for approximately 7 minutes with lid on, stirring occasionally. Stir in the potatoes. Continue to saute for 10-15 more, until the potatoes are soft, stirring regularly with a scraper, to get the little bits off of the bottom of the pan. You do not want to add water. When potatoes are tender enough to eat, add remaining ingredients and the onion mixture. Cook until the tomatoes begin to fall apart. 

3. Serve on its own or over rice.