That reads like a somewhat classic seared tuna. I love sashimi grade seared tuna. Tuna cooked beyond med-rare in the center smells and tastes fishy to me and I'm not a fan of "fishy".
I've been working on a "finishing sauce" to add some extra sauce to teriyaki chicken thighs Sam's club sells seasonally. The sauce on them is a bit sweet which is not usually my jam, but these boneless chicken thighs are outstanding and easy. Just plop them frozen on a pan in the toaster oven and bake. I like to slice them after cooking and put them on a bed of basmati rice, then drizzle with my finishing sauce to give the rice something to play with.
Here is the current recipe. The only thing I haven't nailed is getting it as thick as I want without making it gelatinous. I haven't tried cornstarch yet. I have been trying to balance Xanthan gum but haven't gotten it just right. Too much and it starts getting "snotty". Taste is fine but a loose gelatin is not what I'm looking for. I plan to try Thickitup next before cornstarch. I try to keep stuff like this lower carb but a little cornstarch isn't too much carbs. I use sugar free honey and brown sugar in this as well and I cant detect the artificial sweetener...and I am someone that can taste "sugar free" from a mile away. Real honey and brown sugar will work fine, of course.
Asian finishing sauce
For 2-4 servings
2 tbls Thai mushroom soy
1 tbls regular low sodium soy
2 tbls SF honey
1 tbls rice vinegar
1 tbls chili
garlic sauce or Sambal
1 tsp lime juice
*1 tbls brown sugar or SF sub for making it more sweet
*fresh grated ginger if available
Try xanthan gum or cornstarch slurry for thickening (that's a note to myself)
At serving
*toasted sesame seeds if have
*Chopped green onion or chives if have
This guy gives several options. Not bieng much for creamy sauces with tuna (I do love tartar sauce with fried fish but seared tuna is an entirely different animal), I would probably go with the honey soy, soy ginger lime, ponzu or the balsamic glaze.
I make balsamic reduction every summer for Caprese when the tomatoes are in season (like right now, making Caprese for lunch today) and now my wife is getting harvests from her fig tree and we have started making bites with a fig half, a dollop of goat cheese, a piece of fresh basil leaf pressed on, then wrapped with prosciutto and broiled for a few minutes. Those get plated then drizzled with a little bit of honey and a medium drizzle of balsamic reduction. It takes figs, which are not an impressive flavor on their own, and elevates them in to something more special.
Of course if you like wasabi, there's that wasabi soy sauce slurry I mentioned. That's what I do for all sushi/sahshimi/maki, etc.. I like the wasabi taken to just slightly over the "uncomfortable" line where I need a tissue nearby!