〈夕／ゆう／ユウ／ユー〉〈焼（け）／やけ／ヤケ〉〈空／ぞら／ゾラ〉

Google N-gram Corpus Counts
╭─ーーーーーー─┬────────┬───────╮
│ 夕焼け空　　 │ 59,902 │ 97.1% │
│ 夕焼空　　　 │    827 │  1.3% │ - add
│ 夕やけ空　　 │    542 │  0.9% │ - add
│ ゆうやけ空　 │    204 │  0.3% │ - add
│ 夕焼けぞら　 │     23 │  0.0% │
│ ゆうやけぞら │    178 │  0.3% │
╰─ーーーーーー─┴────────┴───────╯

@@ -5,0 +6,12 @@
+</k_ele>
+<k_ele>
+<keb>夕焼空</keb>
+<ke_inf>&sK;</ke_inf>
+</k_ele>
+<k_ele>
+<keb>夕やけ空</keb>
+<ke_inf>&sK;</ke_inf>
+</k_ele>
+<k_ele>
+<keb>ゆうやけ空</keb>
+<ke_inf>&sK;</ke_inf>

Google N-gram Corpus Counts
╭─ーーーーーー─┬────────┬───────╮
│ 夕焼け空　　 │ 59.902 │ 99.7% │
│ ゆうやけぞら │    178 │  0.3% │
╰─ーーーーーー─┴────────┴───────╯

Luminous: red sky; the sky aglow with the setting sun
GG5: the sky aglow with the setting sun
Chuujiten: red sky (after sundown); the sky aglow with the setting sun

Prog also has that gloss as a second option

.

I'd personally favour having the extensive gloss as well because it gives a much fuller description of the word. But I get that there are probably opinions here contrary to mine.
If it needs to go it needs to go

@@ -11,0 +12 @@
+<gloss>sky aglow with the setting sun</gloss>
@@ -12,0 +14 @@
+<gloss>red sky</gloss>

Progressive