Spicy Rice and Corn Casserole

( 8 ounce ) box of yellow rice (like Zatarain's New Orleans Style)

unsalted butter , divided

( 11 ounce ) can of Mexican corn , undrained

( 10-3/4 ounce ) can of Campbell's Cream of Celery Soup

chopped jalapenos

Kosher salt , only if needed,

freshly cracked black pepper , or to taste

Cajun seasoning (like Slap Ya Mama ), or to taste

overflowing cup