Soak the raw cashews in hot water for at least 15 minutes to soften them. Drain the cashews after soaking.
Chop: While the cashews are soaking, finely chop the onion and 4 garlic cloves.
Heat 1 tbsp olive oil in a large pan that has a lid, and cook the onion and garlic over medium-low heat for about 2 minutes. Add ¼ cup water. Cover the pan, and cook over low heat for about 10 minutes, until the onions are soft. You are not trying to brown the onions.
While the onions are cooking, thaw the spinach. To avoid browning the spinach, thaw on low heat in the microwave until just thawed. Try to avoid getting the spinach hot. Do not drain the spinach.
Blend the spinach mixture: Place the thawed spinach and all the other spinach mixture ingredients plus the drained cashews in a blender. Purée until the mixture is smooth. If you want the texture of some cashew bits, it’s okay to purée a little less.
Cook the halloumi: Once the onions are cooked, move the onions off to the sides, and add the cubed halloumi to the pan. Cook over medium heat, and turn the halloumi occasionally so that it browns on at least a couple sides.
Add the spinach mixture to the pan. Cook for about 2 minutes, until well heated, but not turning brown. Off heat and add lemon juice.
Serve over rice or with a Middle-Eastern flatbread such as lavash or pita.