Add penne pasta and water to the Instant Pot. Cook on high pressure for 4 minutes, then perform a quick release. Drain the pasta and let it cool.
While the pasta cooks, fry the bacon in a pan until crispy. Once done, place the bacon on a paper towel to absorb excess grease, then crumble it.
Chop the romaine lettuce, halve the cherry tomatoes, and thinly slice the red onion.
In a bowl, whisk together ranch dressing, mayonnaise, and Dijon mustard until smooth and creamy.
In a large bowl, mix the cooled pasta, chopped lettuce, tomatoes, red onion, and crumbled bacon.
Pour the dressing over the pasta salad and toss until everything is well coated. Season with salt and black pepper to taste.
Chill the salad in the refrigerator for 30 minutes before serving, or enjoy it immediately for a refreshing, creamy BLT pasta salad!