Adjust rack to top position and preheat oven to 450 degrees. Wash and dry produce.

Halve, peel, and finely dice onion. Trim and halve zucchini lengthwise; scoop out and discard seeds with a spoon.

Heat a drizzle of olive oil in a medium pot over medium-high heat. Add ¾ of the onion; season with salt and pepper. Cook, stirring, until softened, 4-5 minutes.

Add rice and Southwest Spice Blend; stir to coat.

Stir in stock concentrate, 1¼ cups water (2¼ cups for 4 servings), and a big pinch of salt. Bring to a boil, then cover and reduce to a low simmer. Cook until rice is tender, 15-18 minutes.

Keep covered off heat until ready to use in step 5.

Swap in brown rice for jasmine rice; use 1¾ cups water (3½ cups for 4) and a big pinch of salt. Cook until tender, 20-25 minutes. Keep covered off heat until ready to use in step 5. (Save jasmine rice for another use.)

While rice cooks, season zucchini with a drizzle of olive oil, salt, and pepper; rub to evenly coat. Arrange, cut sides down, on a baking sheet.

Roast on top rack until browned and tender, 15-20 minutes.

Heat a drizzle of oil in a large pan over medium-high heat. Add beef*; season with salt and pepper. Cook, breaking up meat into pieces, until browned and cooked through, 4-6 minutes.

Meanwhile, dice tomato. Roughly chop cilantro. Zest and halve lemon.

In a small bowl, combine tomato, half the cilantro, a squeeze of lemon juice to taste, and as much remaining onion as you like. Season with salt and pepper.

In a separate small bowl, combine guacamole, lemon zest, and half the sour cream (save the rest for serving). Add a squeeze of lemon juice to taste. Season with salt and pepper. Add water 1 tsp at a time until mixture reaches a drizzling consistency.

Once zucchini are tender, remove sheet from oven. Heat broiler to high.

Fluff rice with a fork and season with salt and pepper. TIP: Stir in 1 TBSP butter (2 TBSP for 4 servings) for extra richness.

Carefully flip zucchini and stuff with as much rice as will fit (there will be plenty left over; save for serving). Evenly top with pepper jack.

Broil until cheese is melted and lightly browned, 2-3 minutes. TIP: Watch carefully to avoid burning.

Stir beef into rice before stuffing zucchini.

Divide remaining rice between plates and top with stuffed zucchini. Top with avocado crema, pico de gallo, remaining cilantro, and remaining sour cream. Drizzle with hot sauce if desired and serve.