Index: wp-content/themes/twentynineteen/style-editor.css
===================================================================
--- wp-content/themes/twentynineteen/style-editor.css	(revision 58682)
+++ wp-content/themes/twentynineteen/style-editor.css	(working copy)
@@ -1058,6 +1058,9 @@
 }
 
 /** === Blockquote === */
+.wp-block-quote[style*="font-size"] p {
+  font-size: 1em;
+}
 .wp-block-quote:not(.is-large):not(.is-style-large) {
   border-width: 2px;
   border-color: #0073aa;
Index: wp-content/themes/twentynineteen/style-editor.scss
===================================================================
--- wp-content/themes/twentynineteen/style-editor.scss	(revision 58682)
+++ wp-content/themes/twentynineteen/style-editor.scss	(working copy)
@@ -467,7 +467,11 @@
 /** === Blockquote === */
 
 .wp-block-quote {
-
+	&[style*="font-size"] {
+		p {
+		  font-size: 1em;
+		}
+	  }
 	&:not(.is-large):not(.is-style-large) {
 		border-width: 2px;
 		border-color: $color__link;
Index: wp-content/themes/twentynineteen/style-rtl.css
===================================================================
--- wp-content/themes/twentynineteen/style-rtl.css	(revision 58682)
+++ wp-content/themes/twentynineteen/style-rtl.css	(working copy)
@@ -5836,14 +5836,6 @@
   line-height: 1.8;
 }
 
-.entry .entry-content .wp-block-quote cite {
-  /*
-			 * This requires a rem-based font size calculation instead of our normal em-based one,
-			 * because the cite tag sometimes gets wrapped in a p tag. This is equivalent to $font-size_xs.
-			 */
-  font-size: calc(1rem / (1.25 * 1.125));
-}
-
 .entry .entry-content .wp-block-quote.is-large, .entry .entry-content .wp-block-quote.is-style-large {
   margin: 1rem 0;
   padding: 0;
Index: wp-content/themes/twentynineteen/style.css
===================================================================
--- wp-content/themes/twentynineteen/style.css	(revision 58682)
+++ wp-content/themes/twentynineteen/style.css	(working copy)
@@ -5848,13 +5848,6 @@
   line-height: 1.8;
 }
 
-.entry .entry-content .wp-block-quote cite {
-  /*
-			 * This requires a rem-based font size calculation instead of our normal em-based one,
-			 * because the cite tag sometimes gets wrapped in a p tag. This is equivalent to $font-size_xs.
-			 */
-  font-size: calc(1rem / (1.25 * 1.125));
-}
 
 .entry .entry-content .wp-block-quote.is-large, .entry .entry-content .wp-block-quote.is-style-large {
   margin: 1rem 0;