Char grill tomatoes, onion, garlic and serrano pepper until lightly charred. Place tomatoes garlic, serrano pepper, onion in a molcajete (Mexican mortar and pestle) or a food processor and blend until salsa is chunky, season with salt to taste.
Char grill the tortillas on both sides until toasted and crisp.
Char grill Johnsonville® Cheddar Sausage for 10-12 minutes or until heated through, turning links often, remove from grill slice and place on top of tostada.
Serve with red salsa, chopped onion and cilantro.