• In a fine-mesh strainer, rinse the rice.

In a small sauce pot, combine the rice and ¾ cup lightly salted water; bring to a boil. Reduce to a simmer, cover, and cook until the rice is tender and the water is absorbed, 12 to 14 minutes. Fluff with a fork, cover, and keep warm.
While the rice cooks, marinate the chicken.

• Cut a small corner from the chicken packaging; drain off any excess liquid. Transfer to a plate; pat dry with a paper towel.
• Finely chop, press, or grate enough garlic to measure 1 teaspoon.
• Juice half the lemon; cut half into wedges for garnish.

In a medium bowl, stir together the chicken, garlic, lemon juice, and yogurt; season with salt and pepper. Set aside to marinate.
While the chicken marinates, prepare the remaining ingredients.

• Peel and coarsely chop the yellow onion.
• Grate or peel and finely chop the ginger.
• Coarsely chop the cilantro.

In a medium sauce pot over medium-high heat, warm 2 tablespoons oil until hot but not smoking. Add the chicken; cook, stirring occasionally, until browned but not yet cooked through, 2 to 4 minutes. Transfer to a plate. Do not wipe out the pot.

In the same pot used for the chicken, warm the butter or 1 tablespoon oil over medium heat. Add the onion, season with salt, and cook, stirring occasionally, until softened, 4 to 5 minutes. Stir in the ginger, masala spice blend, and as much cayenne as you like; cook until fragrant, about 1 minute. Stir in the tomatoes, coconut milk, and ½ cup water; bring to a boil. Reduce to a simmer; cook, stirring occasionally, until the sauce thickens slightly, 3 to 5 minutes.
Add the chicken; cook, stirring occasionally, until the chicken is cooked through, 1 to 2 minutes. Season to taste with salt and pepper. Remove from the heat; fold in the spinach.

Transfer the rice to individual bowls; top with the chicken and sauce. Garnish with the cilantro; serve with the lemon wedges.