Preheat the oven to 425 degrees F and line two baking sheets with foil.
First prepare the lentils. To a medium pot over high heat add the the water and lentils. Bring to a boil and reduce heat to low. Cover and simmer the lentils for approximately 15-20 minutes, or until the lentils are fork tender (not mushy!) and most of the water has been absorbed. Once cooked, remove from heat (yes, even if all the water has not been absorbed), and drain using a fine mesh strainer. Set aside.
Prepare the salsa- In a medium bowl combine the diced mango, pomegranate seeds, red onion, orange zest, orange juice, lime juice and chopped cilantro. Mix well and cover. Set aside until ready to use.
Transfer chopped cauliflower to baking sheet and drizzle with 1-2 tablespoons olive oil, ground cumin and a generous pinch of salt and pepper. Carefully toss to coat. Transfer baking sheet to the oven and roast cauliflower for approximately 20-25 minutes, or until completely cooked and browning on the top and edges. Remove from oven and set aside.
Meanwhile, as the cauliflower is cooking, start preparing the salsa verde. Start by removing the husks from the tomatillos and rinse them under warm water. Cut each tomatillo in half and place side down on prepared foil-lined baking sheet. To the same sheet add the garlic and jalapeno halves.
Once the cauliflower has finished roasting remove baking sheet from the oven and set oven to broil. Add the baking sheet with the tomatillos and broil for approximately 6-10 minutes, or until the skin of the tomatillos has blackened and the skin of the jalapeños has darkened. Remove from the oven and allow to rest until cool enough to handle.
Remove the garlic cloves from their skin and place in a blender or food processor, along with the tomatillos and jalapeños. Add the lime juice, cilantro and salt and pepper, to taste. Blend until smooth.
Stir in approximately 1/2 cup to 1 cup of the salsa verde in with the cooked lentils. Save any remaining salsa to use as extra.
Assemble each taco with a scoop of lentils, cauliflower florets and fresh mango pomegranate salsa. Add sour cream or shredded cheese, if desired (not shown).