Preheat oven to 350 degrees. Toast panko in a large skillet over medium-high heat until golden, tossing occasionally, about 3 minutes. Transfer to a bowl; let cool, then stir in salt and cheese.
Place a steamer basket in a pot filled with water to just below basket. Bring to a boil, then place cauliflower in basket; cover and steam 10 minutes. Reduce heat to low; steam until cauliflower is fork-tender, 8 to 10 minutes. Transfer to a serving bowl.
Meanwhile, melt butter in a saucepan over medium heat until browned, about 9 minutes. Remove from heat; swirl in paprika. Pour half of brown butter over cauliflower; sprinkle with half of panko mixture. Cut cauliflower into chunks with a paring knife. Pour remaining brown butter over top; sprinkle with remaining panko mixture. Serve.