Indian red lentil and potato dhal

Name: Indian red lentil and potato dhal
Ingredients: 14 ounces Red lentils, ready made; 2 potatoes, medium size; 1 red onion, finely chopped; 1 tablespoon red curry paste; 1/2 teaspoon garam masala; 1/2 teaspoon tumeric; 1/2 teaspoon dried chili flakes; 1 teaspoon indian curry powder; 1 teaspoon sugar; 1 teaspoon minced garlic; 1 teaspoon minced ginger; 7 ounces canned chopped tomatoes; 1/3 cup coconut milk; 1 tablespoon lemon juice; 1 handful chopped cilantro