Salsa Roja

Bahan-bahan (1 porsi)

• 3 to 4 tomatoes (about 1 pound, left whole (I used Roma))
• 1/4 medium white onion (cut through the stem into 2 wedges)
• 1 serrano chile (halved lengthwise, seeds and membranes removed)
• 1 g arlic clove (roughly chopped)
• Juice of 1/2 small lime (about 2 teaspoons)
• 1/2 teaspoon kosher salt (plus additional to taste)
• 1/8 teaspoon ground cumin
• 1/2 cup chopped fresh cilantro (divided)