Season tuna steaks with salt and pepper on both sides.
In a large skillet, heat olive oil over medium-high heat.
Add tuna steaks and sear for 2-3 minutes per side for medium-rare, or cook to desired doneness.
Remove tuna steaks from the skillet and set aside.
In the same skillet, add minced garlic and cook for 1 minute until fragrant.
Pour in heavy cream and bring to a simmer.
Stir in grated Parmesan cheese until melted and the sauce has thickened.
Return the tuna steaks to the skillet and coat them with the creamy garlic sauce.
In a large bowl, toss together mixed salad greens, cherry tomatoes, cucumbers, and red onions.
Drizzle balsamic vinaigrette over the salad and toss to combine.
Serve the tuna steaks with the creamy garlic sauce alongside the mixed salad.