(the food has) the most authentically Japanese flavor
(the food) tastes the closest to actual Japanese food
(the food) tastes the closest to how it tastes in Japan
authentically = 真正に、確かに
actual = 実在の、現実の
how it tastes = the way that it tastes
このtasteは動詞で「味がする」という意味です。
「taste」は名詞でも使えます；「味」という意味で。
例えば「its taste is similar to how food in Japan tastes」（この食べ物の味は日本での食べ物と近いです。）
よくある間違っている英訳は「It has Japan's taste」です。そういうと、日本を食べているとうい感じがします！
This food is excellent! It is nearly identical to true Japanese food.
I have not found another restaurant that makes such authentic Japanese food as yours.
This food is so close to authentic Japanese food.
This food is excellent! It is nearly identical to true Japanese food.
I have not found another restaurant that makes such authentic Japanese food as yours.
You have the best Japanese food I have tasted abroad.
My compliments to the chef. This is superb Japanese food. Almost authentic.
This is the best Japanese food I have tasted outside of Japan.
This food is so close to authentic Japanese food.（この料理は本物の和食にすごく近いです）
This food is excellent! It is nearly identical to true Japanese food.（この料理は素晴らしいです。本物の和食とほとんど同じです）
I have not found another restaurant that makes such authentic Japanese food as yours.（こんなに本物の和食に近い料理を出すレストランは他に知りません）
You have the best Japanese food I have tasted abroad.（日本以外で食べた和食の中でここが一番おいしいです）
My compliments to the chef. This is superb Japanese food. Almost authentic.（シェフによろしくお伝えください。素晴らしい日本料理です。日本で出されるものとほとんど同じです）
This is the best Japanese food I have tasted outside of Japan.（これは日本以外で食べた和食の中で一番おいしいです）
This foreign restaurant serves really good Japanese style food!
"This almost tastes like authentic Japanese food!"
"almost" meaning that the taste is very near to the Japanese flavors
"This is very similar to real Japanese food!"
"similar" meaning, not 100% the same taste but close
"This foreign restaurant serves really good Japanese style food!"
"Japanese style" meaning that it is not made by a Japanese person but they cook Japanese food
"This almost tastes like authentic Japanese food!"（これは本物の和食の味にすごく近いです）
"almost" は、その味が和食にすごく近いことを表します。
"This is very similar to real Japanese food!"（これは本物の和食にすごく近いです）
"similar" は、全く同じ味ではないけど近いことを表します。
"This foreign restaurant serves really good Japanese style food!"（このレストランは本当においしい和食を出します）
"Japanese style" は、日本人が作った料理という意味ではありません、日本の料理という意味です。
This place has the most authentic tasting Japanese food.
The food here is really close to authentic Japanese food.
「authentic」は日本語で「本物」か「本当の」という意味に近いです。
This place has the most authentic tasting Japanese food.
（この店は一番日本の味に近い。）
The food here is really close to authentic Japanese food.
（この店の食料は日本の味にすごく近い。）
This restaurant has the most authentic Japanese food
The food here tastes just like it does in Japan
Authentic means it is done in a traditional way as in that country and origin and is very like traditional Japanese food
A simple way to espress this is 'the food here tastes just like it does in Japan'
Authentic とは、その国のもともとある伝統的な方法でされる、つまり伝統的な和食のようだ、という意味です。
シンプルな言い方は、'the food here tastes just like it does in Japan'（ここの料理は、日本の味そのものだ。）でしょう。
Of all of the places I've tried, this place serves Japanese dishes that are the closest to the genuine thing.
I haven't tasted Japanese food as authentic as this anywhere else while traveling abroad.
1.
Saying that one has tried a place is a way to indicate that he/she went to the restaurant in order to experience the type of food that it serves. The "genuine thing" expresses that the food is very similar and almost identical to the food served in its original location.
2.
In order to indicate that one has experienced the real and original thing (Japanese food in this case), saying "as authentic" is a way to express that. In order to make a point to explain that one is speaking specifically about restaurants that are outside of Japan, it is important to say "while traveling abroad."
The taste of food here is the closest to authentic Japanese as I have ever experienced abroad
The food served in this place has a real authentic Japanese taste
While talking about a certain Japanese restaurant (abroad) and also the fact that you have eaten at many Japanese restaurants (abroad) before, you want to say that this restaurant is the closest to the real authentic Japanese taste. Either of the above suggestions is adequate for that scenario.
アメリカ合衆国 
南アフリカ 
イギリス 
