Slice jalapeños in half, lengthwise, and use a spoon to scoop out ribs and seeds; discard.

Prepare a grill pan for medium-high heat. Coat jalapeños and ear of corn with cooking spray or lightly brush with oil. Grill, turning occasionally, until jalapeño is charred and kernels of corn are tender and charred in spots, 5 to 6 minutes for jalapeño, 10 to 12 minutes for corn. Let cool slightly, then cut kernels from cob.

Place charred jalapeño halves in a food processor or blender along with chickpeas, tahini, 2 Tbsp. of the lime juice, garlic, salt, and cumin. Blend on HIGH, and with motor running, gradually stream in 1/3 cup olive oil. Continue blending for 3 minutes, stopping to scrap down the sides as needed, until smooth. Transfer hummus to a wide-rimmed bowl.

Combine charred corn kernels with cilantro and feta in a small bowl. Stir in remaining 1 Tbsp. lime juice and 1 1/2 Tbsp. olive oil. Spoon corn mixture over hummus.