Normally ponzu sauce is traditionally made with yuzu citrus in Japan, but I have an old Meyer lemon tree that produces fabulous lemons throughout the year. I try to use the lemons in many recipes and this is my own version of Ponzu Sauce using Meyer lemons instead of yuzu limes/lemons. Although I planted yuzu tree a year ago it is still not producing yet and when it is finally producing I would also make homemade ponzu sauce using yuzu too, but until then this is the only ponzu sauce I like. You can certainly use any type of lemons or combination lemons and limes/oranges. Unlike commercial based ponzu sauces which are very sweet and more vinegar than real juice, I think this version has much more depth. For 3/4 C juice, I usually end up using 5-6 lemons depending on their sizes. Bonito flakes is known as Katsuobushi in Japanese and it is dried bonito fish flakes found in Japanese markets. If you are unable to find kombu or katsuobushi, please use any instant dashi for this purpose. The taste will not be as good, but it will surpass the overly vinegar/sugar taste of commercial ponzu sauce. If using instant dashi, I would follow the direction on amount per liquid found with the products. Depending on how strong you like the taste of dashi, you can use either 1 to 1 1/2 C bonito flakes for this recipe. Note to those who never tried ponzu: This sauce is very versatile and you can use it top any steamed veggies, fish, meat, or tofu. You can also add a bit of oil to make into traditional salad dressing but go easy on oil!